A significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. Multi-cellular life also began to appear on land in the form of small, bryophyte-like and vascular plants that grew beside lakes, streams, and coastlines, and terrestrial arthropods are also first found on land during the Silurian. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian.

The Silurian system was first identified by British geologist Roderick Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick, who had named the period of his study the Cambrian, from the Latin name for Wales. This naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures (cf. Geologic map of Wales, Map of pre-Roman tribes of Wales). In 1835 the two men presented a joint paper, under the title On the Silurian and Cambrian Systems, Exhibiting the Order in which the Older Sedimentary Strata Succeed each other in England and Wales, which was the germ of the modern geological time scale. As it was first identified, the "Silurian" series when traced farther afield quickly came to overlap Sedgwick's "Cambrian" sequence, however, provoking furious disagreements that ended the friendship. Charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was "Gotlandian" after the strata of the Baltic island of Gotland.

The French geologist Joachim Barrande, building on Murchison's work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge, he divided the Silurian rocks of Bohemia into eight stages. His interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian, despite these modifications in the original groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils.

The Ludlow, lasting from 427.4 ± 1.5 to 423 ± 2.8 mya, comprises the Gorstian stage, lasting until 425.6million years ago, and the Ludfordian stage. It is named for the town of Ludlow (and neighbouring Ludford) in Shropshire, England.

The Pridoli, lasting from 423 ± 1.5 to 419.2 ± 2.8 mya, is the final and shortest epoch of the Silurian. It is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a cadastral field area.[11]

With the supercontinentGondwana covering the equator and much of the southern hemisphere, a large ocean occupied most of the northern half of the globe,[13] the high sea levels of the Silurian and the relatively flat land (with few significant mountain belts) resulted in a number of island chains, and thus a rich diversity of environmental settings.[13]

During the Silurian, Gondwana continued a slow southward drift to high southern latitudes, but there is evidence that the Silurian icecaps were less extensive than those of the late Ordovician glaciation, the southern continents remained united during this period. The melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity, the continents of Avalonia, Baltica, and Laurentiadrifted together near the equator, starting the formation of a second supercontinent known as Euramerica.

When the proto-Europe collided with North America, the collision folded coastal sediments that had been accumulating since the Cambrian off the east coast of North America and the west coast of Europe, this event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway. At the end of the Silurian, sea levels dropped again, leaving telltale basins of evaporites extending from Michigan to West Virginia, and the new mountain ranges were rapidly eroded, the Teays River, flowing into the shallow mid-continental sea, eroded Ordovician Period strata, forming deposits of Silurian strata in northern Ohio and Indiana.

The Silurian period enjoyed relatively stable and warm temperatures, in contrast with the extreme glaciations of the Ordovician before it, and the extreme heat of the ensuing Devonian.[13] Sea levels rose from their Hirnantian low throughout the first half of the Silurian; they subsequently fell throughout the rest of the period, although smaller scale patterns are superimposed on this general trend; fifteen high-stands can be identified, and the highest Silurian sea level was probably around 140 m higher than the lowest level reached.[13]

During this period, the Earth entered a long, warm greenhouse phase, supported by high CO2 levels of 4500 ppm, and warm shallow seas covered much of the equatorial land masses. Early in the Silurian, glaciers retreated back into the South Pole until they almost disappeared in the middle of Silurian, the period witnessed a relative stabilization of the Earth's general climate, ending the previous pattern of erratic climatic fluctuations. Layers of broken shells (called coquina) provide strong evidence of a climate dominated by violent storms generated then as now by warm sea surfaces. Later in the Silurian, the climate cooled slightly, but closer to the Silurian-Devonian boundary, the climate became warmer.[citation needed]

The climate and carbon cycle appears to be rather unsettled during the Silurian, which has a higher concentration of isotopic excursions than any other period,[13] the Ireviken event, Mulde event and Lau event each represent isotopic excursions following a minor mass extinction[14] and associated with rapid sea-level change, in addition to the larger extinction at the end of the Silurian.[13] Each one leaves a similar signature in the geological record, both geochemically and biologically; pelagic (free-swimming) organisms were particularly hard hit, as were brachiopods, corals and trilobites, and extinctions rarely occur in a rapid series of fast bursts.[13]

The Silurian was the first period to see megafossils of extensive terrestrial biota, in the form of moss-like miniature forests along lakes and streams. However, the land fauna did not have a major impact on the Earth until it diversified in the Devonian.[13]

The first fossil records of vascular plants, that is, land plants with tissues that carry water and food, appeared in the second half of the Silurian period,[15] the earliest known representatives of this group are Cooksonia. Most of the sediments containing Cooksonia are marine in nature. Preferred habitats were likely along rivers and streams. Baragwanathia appears to be almost as old, dating to the early Ludlow (420 million years) and has branching stems and needle-like leaves of 10–20 cm. The plant shows a high degree of development in relation to the age of its fossil remains. Fossils of this plant have been recorded in Australia,[16] Canada[17] and China.[18]Eohostimella heathana is an early, probably terrestrial, "plant" known from compression fossils[19] of early Silurian (Llandovery) age.[20] The chemistry of its fossils is similar to that of fossilised vascular plants, rather than algae.[19]

Reef abundance was patchy; sometimes fossils are frequent but at other points are virtually absent from the rock record.[13]

The earliest known animals fully adapted to terrestrial conditions appear during the Mid Silurian, including the millipede Pneumodesmus,[10] some evidence also suggests the presence of predatory trigonotarbid arachnoids and myriapods in Late Silurian facies.[23] Predatory invertebrates would indicate that simple food webs were in place that included non-predatory prey animals. Extrapolating back from Early Devonian biota, Andrew Jeram et al. in 1990[24] suggested a food web based on as yet undiscovered detritivores and grazers on micro-organisms.[25]

^Samtleben, C.; Munnecke, A.; Bickert, T. (2000). "Development of facies and C/O-isotopes in transects through the Ludlow of Gotland: Evidence for global and local influences on a shallow-marine environment". Facies. 43: 1. doi:10.1007/BF02536983.

^Lang, W.H.; Cookson, I.C. (1935). "On a flora, including vascular land plants, associated with Monograptus, in rocks of Silurian age, from Victoria, Australia". Philosophical Transactions of the Royal Society of London B. 224 (517): 421–449. doi:10.1098/rstb.1935.0004.

1.
Cambrian
–
The Cambrian Period was the first geological period of the Paleozoic Era, of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million years ago to the beginning of the Ordovician Period 485.4 mya and its subdivisions, and its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latinised form of Cymru, the Welsh name for Wales, as a result, our understanding of the Cambrian biology surpasses that of some later periods. The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, most of the continents were probably dry and rocky due to a lack of vegetation. Shallow seas flanked the margins of several continents created during the breakup of the supercontinent Pannotia, the seas were relatively warm, and polar ice was absent for much of the period. The United States Federal Geographic Data Committee uses a barred capital C ⟨Є⟩ character similar to the capital letter Ukrainian Ye ⟨Є⟩ to represent the Cambrian Period, the proper Unicode character is U+A792 Ꞓ LATIN CAPITAL LETTER C WITH BAR. Despite the long recognition of its distinction from younger Ordovician Period rocks and older Supereon Precambrian rocks, the base of the Cambrian lies atop a complex assemblage of trace fossils known as the Treptichnus pedum assemblage. Pedum in Namibia, Spain and Newfoundland, and possibly, in the western USA, the stratigraphic range of T. pedum overlaps the range of the Ediacaran fossils in Namibia, and probably in Spain. The Cambrian Period followed the Ediacaran Period and was followed by the Ordovician Period, the Cambrian is divided into four epochs and ten ages. Currently only two series and five stages are named and have a GSSP, because the international stratigraphic subdivision is not yet complete, many local subdivisions are still widely used. In some of these subdivisions the Cambrian is divided into three epochs with locally differing names – the Early Cambrian, Middle Cambrian and Furongian, rocks of these epochs are referred to as belonging to the Lower, Middle, or Upper Cambrian. Trilobite zones allow biostratigraphic correlation in the Cambrian, each of the local epochs is divided into several stages. The International Commission on Stratigraphy list the Cambrian period as beginning at 541 million years ago, the lower boundary of the Cambrian was originally held to represent the first appearance of complex life, represented by trilobites. The recognition of small shelly fossils before the first trilobites, and Ediacara biota substantially earlier and this formal designation allowed radiometric dates to be obtained from samples across the globe that corresponded to the base of the Cambrian. Early dates of 570 million years ago quickly gained favour, though the used to obtain this number are now considered to be unsuitable. A more precise date using modern radiometric dating yield a date of 541 ±0.3 million years ago, most continental land was clustered in the Southern Hemisphere at this time, but was drifting north. Large, high-velocity rotational movement of Gondwana appears to have occurred in the Early Cambrian, the sea levels fluctuated somewhat, suggesting there were ice ages, associated with pulses of expansion and contraction of a south polar ice cap. In Baltoscandia a Lower Cambrian transgression transformed large swathes of the Sub-Cambrian peneplain into a epicontinental sea, the Earth was generally cold during the early Cambrian, probably due to the ancient continent of Gondwana covering the South Pole and cutting off polar ocean currents

2.
Ordovician
–
The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.2 million years from the end of the Cambrian Period 485.4 million years ago to the start of the Silurian Period 443.8 Mya. Lapworth recognized that the fauna in the disputed strata were different from those of either the Cambrian or the Silurian periods. It received international sanction in 1960, when it was adopted as a period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier Cambrian period, invertebrates, namely molluscs and arthropods, dominated the oceans. The Great Ordovician Biodiversification Event considerably increased the diversity of life, fish, the worlds first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period. Life had yet to diversify on land, about 100 times as many meteorites struck the Earth during the Ordovician compared with today. The Ordovician Period began with a major extinction called the Cambrian–Ordovician extinction event and it lasted for about 42 million years and ended with the Ordovician–Silurian extinction event, about 443.8 Mya which wiped out 60% of marine genera. The dates given are recent radiometric dates and vary slightly from those found in other sources and this second period of the Paleozoic era created abundant fossils that became major petroleum and gas reservoirs. The boundary chosen for the beginning of both the Ordovician Period and the Tremadocian stage is highly significant and it correlates well with the occurrence of widespread graptolite, conodont, and trilobite species. The base of the Tremadocian allows scientists to relate these species not only to each other and this makes it easier to place many more species in time relative to the beginning of the Ordovician Period. A number of terms have been used to subdivide the Ordovician Period. In 2008, the ICS erected an international system of subdivisions. There exist Baltoscandic, British, Siberian, North American, Australian, the Ordovician Period in Britain was traditionally broken into Early, Middle and Late epochs. The corresponding rocks of the Ordovician System are referred to as coming from the Lower, Middle, the Floian corresponds to the lower Arenig, the Arenig continues until the early Darriwilian, subsuming the Dapingian. The Llanvirn occupies the rest of the Darriwilian, and terminates with it at the base of the Late Ordovician. The Sandbian represents the first half of the Caradoc, the Caradoc ends in the mid-Katian, during the Ordovician, the southern continents were collected into Gondwana. Gondwana started the period in equatorial latitudes and, as the period progressed, drifted toward the South Pole, the small continent Avalonia separated from Gondwana and began to move north towards Baltica and Laurentia, opening the Rheic Ocean between Gondwana and Avalonia

Ordovician
–
External mold of Ordovician bivalve showing that the original aragonite shell dissolved on the sea floor, leaving a cemented mold for biological encrustation (Waynesville Formation of Franklin County, Indiana).
Ordovician
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A diorama depicting Ordovician flora and fauna.
Ordovician
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Nautiloids like Orthoceras were among the largest predators in the Ordovician.
Ordovician
–
Fossiliferous limestone slab from the Liberty Formation (Upper Ordovician) of Caesar Creek State Park near Waynesville, Ohio.

3.
Devonian
–
The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian,419.2 million years ago, to the beginning of the Carboniferous,358.9 Mya. It is named after Devon, England, where rocks from this period were first studied, the first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents, by the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods also became well-established, Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fish. The first ray-finned and lobe-finned bony fish appeared, while the placodermi began dominating almost every aquatic environment. The ancestors of all four-limbed vertebrates began adapting to walking on land, as their strong pectoral, in the oceans, primitive sharks became more numerous than in the Silurian and Late Ordovician. The first ammonites, species of molluscs, appeared, trilobites, the mollusk-like brachiopods and the great coral reefs, were still common. The Late Devonian extinction which started about 375 million years ago severely affected marine life, killing off all placodermi, and all trilobites, save for a few species of the order Proetida. The palaeogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, while the rock beds that define the start and end of the Devonian period are well identified, the exact dates are uncertain. According to the International Commission on Stratigraphy, the Devonian extends from the end of the Silurian 419.2 Mya, another common term is Age of the Fishes, referring to the evolution of several major groups of fish that took place during the period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian, Breconian and Farlovian stages, in the Late Devonian, by contrast, arid conditions were less prevalent across the world and temperate climates were more common. The Devonian Period is formally broken into Early, Middle and Late subdivisions, the rocks corresponding to those epochs are referred to as belonging to the Lower, Middle and Upper parts of the Devonian System. Early Devonian The Early Devonian lasted from 419.2 ±2.8 to 393.3 ±2.5 and began with the Lochkovian stage, which lasted until the Pragian. It spanned from 410.8 ±2.8 to 407.6 ±2.5, and was followed by the Emsian, which lasted until the Middle Devonian began,393. 3±2.7 million years ago. Middle Devonian The Middle Devonian comprised two subdivisions, first the Eifelian, which gave way to the Givetian 387. 7±2.7 million years ago. Late Devonian Finally, the Late Devonian started with the Frasnian,382.7 ±2.8 to 372.2 ±2.5, during which the first forests took shape on land. The first tetrapods appeared in the record in the ensuing Famennian subdivision. This lasted until the end of the Devonian,358. 9±2.5 million years ago, the Devonian was a relatively warm period, and probably lacked any glaciers

Devonian
–
The rocks of Lummaton Quarry in Torquay in Devon played an early role in defining the Devonian period.
Devonian
–
Dunkleosteus, one of the largest armoured fish to ever roam the planet, lived during the late Devonian
Devonian
–
Enrolled phacopid trilobite from the Devonian of Ohio
Devonian
–
The common tabulate coral Aulopora from the Middle Devonian of Ohio – view of colony origin encrusting a brachiopod valve

4.
Carboniferous
–
The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period,298.9 Mya. The name Carboniferous means coal-bearing and derives from the Latin words carbō and ferō, and was coined by geologists William Conybeare and William Phillips in 1822. Based on a study of the British rock succession, it was the first of the system names to be employed. The Carboniferous is often treated in North America as two periods, the earlier Mississippian and the later Pennsylvanian. Terrestrial life was established by the Carboniferous period. Amphibians were the dominant land vertebrates, of one branch would eventually evolve into amniotes. Arthropods were also common, and many were much larger than those of today. Vast swaths of forest covered the land, which would eventually be laid down, the atmospheric content of oxygen also reached their highest levels in geological history during the period, 35% compared with 21% today, allowing terrestrial invertebrates to evolve to great size. A major marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred in the middle of the period, the later half of the period experienced glaciations, low sea level, and mountain building as the continents collided to form Pangaea. In the United States the Carboniferous is usually broken into Mississippian and Pennsylvanian subperiods, the Silesian is roughly contemporaneous with the late Mississippian Serpukhovian plus the Pennsylvanian. In Britain the Dinantian is traditionally known as the Carboniferous Limestone, the Namurian as the Millstone Grit, and the Westphalian as the Coal Measures and Pennant Sandstone. There was also a drop in south polar temperatures, southern Gondwanaland was glaciated throughout the period and these conditions apparently had little effect in the deep tropics, where lush swamps, later to become coal, flourished to within 30 degrees of the northernmost glaciers. Mid-Carboniferous, a drop in sea level precipitated a major extinction, one that hit crinoids. This sea level drop and the unconformity in North America separate the Mississippian subperiod from the Pennsylvanian subperiod. This happened about 323 million years ago, at the onset of the Permo-Carboniferous Glaciation, the Carboniferous was a time of active mountain-building, as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America–Europe along the present line of eastern North America, in the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China, the Late Carboniferous Pangaea was shaped like an O. There were two major oceans in the Carboniferous—Panthalassa and Paleo-Tethys, which was inside the O in the Carboniferous Pangaea, other minor oceans were shrinking and eventually closed - Rheic Ocean, the small, shallow Ural Ocean and Proto-Tethys Ocean

5.
Permian
–
The Permian is a geologic period and system which spans 46.7 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic Period 252.2 Mya. It is the last period of the Paleozoic Era, the following Triassic Period belongs to the Mesozoic Era, the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the groups of the mammals, turtles, lepidosaurs. The world at the time was dominated by two known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior, amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors. The Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earths history, in which nearly 90% of marine species and it would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian-Triassic extinction event was protracted, on land, the term Permian was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil, the region now lies in the Perm Krai of Russia. This could have in part caused the extinctions of marine species at the end of the period by severely reducing shallow coastal areas preferred by many marine organisms. During the Permian, all the Earths major landmasses were collected into a supercontinent known as Pangaea. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, a new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmass interiors experience climates with extreme variations of heat and cold, deserts seem to have been widespread on Pangaea. Such dry conditions favored gymnosperms, plants with seeds enclosed in a cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian, the climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an Ice Age, glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continents interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles, Permian marine deposits are rich in fossil mollusks, echinoderms, and brachiopods. By the close of the Permian, trilobites and a host of other groups became extinct. Terrestrial life in the Permian included diverse plants, fungi, arthropods, the period saw a massive desert covering the interior of Pangaea

6.
Cretaceous
–
The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era, the Cretaceous Period is usually abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites and rudists, during this time, new groups of mammals and birds, as well as flowering plants, appeared. The Cretaceous ended with a mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, the name Cretaceous was derived from Latin creta, meaning chalk. The Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series, in older literature the Cretaceous is sometimes divided into three series, Neocomian, Gallic and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide, in many parts of the world, alternative local subdivisions are still in use. As with other geologic periods, the rock beds of the Cretaceous are well identified. No great extinction or burst of diversity separates the Cretaceous from the Jurassic and this layer has been dated at 66.043 Ma. A140 Ma age for the Jurassic-Cretaceous boundary instead of the usually accepted 145 Ma was proposed in 2014 based on a study of Vaca Muerta Formation in Neuquén Basin. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a first step toward formally changing the age in the International Union of Geological Sciences, due to the high sea level there was extensive space for such sedimentation. Because of the young age and great thickness of the system. Chalk is a type characteristic for the Cretaceous. It consists of coccoliths, microscopically small calcite skeletons of coccolithophores, the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not easily consolidated and the Chalk Group still consists of sediments in many places. The group also has other limestones and arenites, among the fossils it contains are sea urchins, belemnites, ammonites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is usually a marine system consisting of competent limestone beds or incompetent marls

Cretaceous
–
Drawing of fossil jaws of Mosasaurus hoffmanni, from the Maastrichtian of Dutch Limburg, by Dutch geologist Pieter Harting (1866).
Cretaceous
–
Although the first representatives of leafy trees and true grasses emerged in the Cretaceous, the flora was still dominated by conifers like Araucaria (Here: Modern Araucaria araucana in Chile).
Cretaceous
–
Tyrannosaurus rex, one of the largest land predators of all time, lived during the late Cretaceous.
Cretaceous
–
Up to 2 m-long Velociraptor was likely feathered and roamed the late Cretaceous.

7.
Paleogene
–
The Paleogene is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 million years ago to the beginning of the Neogene Period 23.03 Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon and this period consists of the Paleocene, Eocene and Oligocene epochs. The terms Paleogene System and lower Tertiary System are applied to the rocks deposited during the Paleogene Period. By dividing the Tertiary Period into two periods instead of directly into five epochs, the periods are more comparable to the duration of periods of the preceding Mesozoic and Paleozoic Eras. The trend was caused by the formation of the Antarctic Circumpolar Current. During the Paleogene, the continued to drift closer to their current positions. India was in the process of colliding with Asia, subsequently forming the Himalayas, the Atlantic Ocean continued to widen by a few centimeters each year. Africa was moving north to meet with Europe and form the Mediterranean, inland seas retreated from North America early in the period. Australia had also separated from Antarctica and was drifting towards Southeast Asia, mammals began a rapid diversification during this period. Some of these mammals would evolve into forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial. Those that took to the oceans became modern cetaceans, while those that took to the trees became primates, the group to which humans belong. Birds, which were well established by the end of the Cretaceous. In comparison to birds and mammals, most other branches of life remained unchanged during this period. As the Earth cooled, tropical plants became less numerous and were now restricted to equatorial regions, deciduous plants, which could survive through the seasonal climates the world was now experiencing, became more common. The Paleogene is notable in the context of offshore oil drilling, and especially in Gulf of Mexico oil exploration and these rock formations represent the current cutting edge of deep-water oil discovery. Lower Tertiary explorations to date include, Kaskida Oil Field Tiber Oil Field Jack 2 Paleogene Microfossils, 180+ images of Foraminifera

8.
Oxygen
–
Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the group on the periodic table and is a highly reactive nonmetal. By mass, oxygen is the third-most abundant element in the universe, after hydrogen, at standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O2. This is an important part of the atmosphere and diatomic oxygen gas constitutes 20. 8% of the Earths atmosphere, additionally, as oxides the element makes up almost half of the Earths crust. Most of the mass of living organisms is oxygen as a component of water, conversely, oxygen is continuously replenished by photosynthesis, which uses the energy of sunlight to produce oxygen from water and carbon dioxide. Oxygen is too reactive to remain a free element in air without being continuously replenished by the photosynthetic action of living organisms. Another form of oxygen, ozone, strongly absorbs ultraviolet UVB radiation, but ozone is a pollutant near the surface where it is a by-product of smog. At low earth orbit altitudes, sufficient atomic oxygen is present to cause corrosion of spacecraft, the name oxygen was coined in 1777 by Antoine Lavoisier, whose experiments with oxygen helped to discredit the then-popular phlogiston theory of combustion and corrosion. One of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle, Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philos work by observing that a portion of air is consumed during combustion and respiration, Oxygen was discovered by the Polish alchemist Sendivogius, who considered it the philosophers stone. In the late 17th century, Robert Boyle proved that air is necessary for combustion, English chemist John Mayow refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus. From this he surmised that nitroaereus is consumed in both respiration and combustion, Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract De respiratione. Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as a chemical element. This may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory, which was then the favored explanation of those processes. Established in 1667 by the German alchemist J. J. Becher, one part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx. The fact that a substance like wood gains overall weight in burning was hidden by the buoyancy of the combustion products

Oxygen
–
Spectral lines of oxygen
Oxygen
Oxygen
–
A trickle of liquid oxygen is deflected by a magnetic field, illustrating its paramagnetic property
Oxygen
–
Oxygen discharge (spectrum) tube. The green color is similar to the color of an "aurora borealis"

9.
Ludlow epoch
–
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period,419.2 Mya. As with other periods, the rock beds that define the periods start and end are well identified. The base of the Silurian is set at a major Ordovician-Silurian extinction event when 60% of marine species were wiped out, a significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian, the Silurian system was first identified by British geologist Sir Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick and this naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures. As it was first identified, the Silurian series when traced farther afield quickly came to overlap Sedgwicks Cambrian sequence, however, charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was Gotlandian after the strata of the Baltic island of Gotland, the French geologist Joachim Barrande, building on Murchisons work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages and his interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils. The epoch is named for the town of Llandovery in Carmarthenshire, the Wenlock, which lasted from 433.4 ±1.5 to 427.4 ±2.8 mya, is subdivided into the Sheinwoodian and Homerian ages. It is named after Wenlock Edge in Shropshire, England, during the Wenlock, the oldest known tracheophytes of the genus Cooksonia, appear. The first terrestrial animals also appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ±1.5 to 423 ±2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and it is named for the town of Ludlow in Shropshire, England. The Pridoli, lasting from 423 ±1.5 to 419.2 ±2.8 mya, is the final and it is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a field area. The high sea levels of the Silurian and the flat land resulted in a number of island chains. The southern continents remained united during this period, the melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia, Baltica, and Laurentia drifted together near the equator and this event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway

10.
Pridoli epoch
–
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period,419.2 Mya. As with other periods, the rock beds that define the periods start and end are well identified. The base of the Silurian is set at a major Ordovician-Silurian extinction event when 60% of marine species were wiped out, a significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian, the Silurian system was first identified by British geologist Sir Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick and this naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures. As it was first identified, the Silurian series when traced farther afield quickly came to overlap Sedgwicks Cambrian sequence, however, charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was Gotlandian after the strata of the Baltic island of Gotland, the French geologist Joachim Barrande, building on Murchisons work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages and his interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils. The epoch is named for the town of Llandovery in Carmarthenshire, the Wenlock, which lasted from 433.4 ±1.5 to 427.4 ±2.8 mya, is subdivided into the Sheinwoodian and Homerian ages. It is named after Wenlock Edge in Shropshire, England, during the Wenlock, the oldest known tracheophytes of the genus Cooksonia, appear. The first terrestrial animals also appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ±1.5 to 423 ±2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and it is named for the town of Ludlow in Shropshire, England. The Pridoli, lasting from 423 ±1.5 to 419.2 ±2.8 mya, is the final and it is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a field area. The high sea levels of the Silurian and the flat land resulted in a number of island chains. The southern continents remained united during this period, the melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia, Baltica, and Laurentia drifted together near the equator and this event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway

11.
Telychian
–
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period,419.2 Mya. As with other periods, the rock beds that define the periods start and end are well identified. The base of the Silurian is set at a major Ordovician-Silurian extinction event when 60% of marine species were wiped out, a significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian, the Silurian system was first identified by British geologist Sir Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick and this naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures. As it was first identified, the Silurian series when traced farther afield quickly came to overlap Sedgwicks Cambrian sequence, however, charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was Gotlandian after the strata of the Baltic island of Gotland, the French geologist Joachim Barrande, building on Murchisons work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages and his interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils. The epoch is named for the town of Llandovery in Carmarthenshire, the Wenlock, which lasted from 433.4 ±1.5 to 427.4 ±2.8 mya, is subdivided into the Sheinwoodian and Homerian ages. It is named after Wenlock Edge in Shropshire, England, during the Wenlock, the oldest known tracheophytes of the genus Cooksonia, appear. The first terrestrial animals also appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ±1.5 to 423 ±2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and it is named for the town of Ludlow in Shropshire, England. The Pridoli, lasting from 423 ±1.5 to 419.2 ±2.8 mya, is the final and it is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a field area. The high sea levels of the Silurian and the flat land resulted in a number of island chains. The southern continents remained united during this period, the melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia, Baltica, and Laurentia drifted together near the equator and this event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway

12.
Ludfordian
–
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period,419.2 Mya. As with other periods, the rock beds that define the periods start and end are well identified. The base of the Silurian is set at a major Ordovician-Silurian extinction event when 60% of marine species were wiped out, a significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian, the Silurian system was first identified by British geologist Sir Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick and this naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures. As it was first identified, the Silurian series when traced farther afield quickly came to overlap Sedgwicks Cambrian sequence, however, charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was Gotlandian after the strata of the Baltic island of Gotland, the French geologist Joachim Barrande, building on Murchisons work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages and his interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils. The epoch is named for the town of Llandovery in Carmarthenshire, the Wenlock, which lasted from 433.4 ±1.5 to 427.4 ±2.8 mya, is subdivided into the Sheinwoodian and Homerian ages. It is named after Wenlock Edge in Shropshire, England, during the Wenlock, the oldest known tracheophytes of the genus Cooksonia, appear. The first terrestrial animals also appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ±1.5 to 423 ±2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and it is named for the town of Ludlow in Shropshire, England. The Pridoli, lasting from 423 ±1.5 to 419.2 ±2.8 mya, is the final and it is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a field area. The high sea levels of the Silurian and the flat land resulted in a number of island chains. The southern continents remained united during this period, the melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia, Baltica, and Laurentia drifted together near the equator and this event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway

13.
Vascular plants
–
They also have a specialized non-lignified tissue to conduct products of photosynthesis. Vascular plants include the clubmosses, horsetails, ferns, gymnosperms and angiosperms, scientific names for the group include Tracheophyta and Tracheobionta. Vascular plants are distinguished by two characteristics, Vascular plants have vascular tissues which distribute resources through the plant. This feature allows vascular plants to evolve to a larger size than non-vascular plants, in vascular plants, the principal generation phase is the sporophyte, which is usually diploid with two sets of chromosomes per cell. Only the germ cells and gametophytes are haploid, by contrast, the principal generation phase in non-vascular plants is the gametophyte, which is haploid with one set of chromosomes per cell. In these plants, only the spore stalk and capsule are diploid, in other words, elaboration of the spore stalk enabled the production of more spores, and enabled the development of the ability to release them higher and to broadcast them farther. Such developments may include more photosynthetic area for the structure, the ability to grow independent roots, woody structure for support. A proposed phylogeny of the plants after Kenrick and Crane is as follows. Pteridophyta from Smith et al. and lycophytes and ferns by Christenhusz et al and this phylogeny is supported by several molecular studies. Other researchers state that taking fossils into account leads to different conclusions, water and nutrients in the form of inorganic solutes are drawn up from the soil by the roots and transported throughout the plant by the xylem. Organic compounds such as produced by photosynthesis in leaves are distributed by the phloem sieve tube elements. The xylem consists of vessels in flowering plants and tracheids in other vascular plants, a tracheid cell wall usually contains the polymer lignin. The phloem however consists of living cells called sieve-tube members, between the sieve-tube members are sieve plates, which have pores to allow molecules to pass through. Sieve-tube members lack such organs as nuclei or ribosomes, but cells next to them, the most abundant compound in all plants, as in all cellular organisms, is water which serves an important structural role and a vital role in plant metabolism. Transpiration is the process of water movement within plant tissues. Water is constantly transpired from the plant through its stomata to the atmosphere, the movement of water out of the leaf stomata creates a transpiration pull or tension in the water column in the xylem vessels or tracheids. The pull is the result of surface tension within the cell walls of the mesophyll cells. The draw of water upwards may be passive and can be assisted by the movement of water into the roots via osmosis

14.
Arthropods
–
An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and jointed appendages. Arthropods form the phylum Arthropoda, which includes the insects, arachnids, myriapods, arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages, the rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Their versatility has enabled them to become the most species-rich members of all guilds in most environments. They have over a million described species, making up more than 80% of all described living species, some of which. Arthropods range in size from the microscopic crustacean Stygotantulus up to the Japanese spider crab, arthropods primary internal cavity is a hemocoel, which accommodates their internal organs, and through which their haemolymph – analogue of blood – circulates, they have open circulatory systems. Like their exteriors, the organs of arthropods are generally built of repeated segments. Their nervous system is ladder-like, with paired ventral nerve cords running through all segments and their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus. The respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum to which they belong, arthropods also have a wide range of chemical and mechanical sensors, mostly based on modifications of the many setae that project through their cuticles. Aquatic species use internal or external fertilization. Almost all arthropods lay eggs, but scorpions give birth to live young after the eggs have hatched inside the mother, arthropod hatchlings vary from miniature adults to grubs and caterpillars that lack jointed limbs and eventually undergo a total metamorphosis to produce the adult form. The level of care for hatchlings varies from nonexistent to the prolonged care provided by scorpions. The evolutionary ancestry of arthropods dates back to the Cambrian period, the group is generally regarded as monophyletic, and many analyses support the placement of arthropods with cycloneuralians in a superphylum Ecdysozoa. Overall however, the relationships of Metazoa are not yet well resolved. Likewise, the relationships between various groups are still actively debated. Arthropods contribute to the food supply both directly as food, and more importantly indirectly as pollinators of crops. Some species are known to spread disease to humans, livestock. The word arthropod comes from the Greek ἄρθρον árthron, joint, and πούς pous, i. e. foot or leg, arthropods are invertebrates with segmented bodies and jointed limbs

Arthropods
Arthropods
–
Head
Arthropods
–
Cicada climbing out of its exoskeleton while attached to tree
Arthropods
–
Head of a wasp with three ocelli (centre), and compound eyes at the left and right

15.
Unicellular organism
–
A unicellular organism, also known as a single-celled organism, is an organism that consists of only one cell, unlike a multicellular organism that consists of more than one cell. Historically, simple unicellular organisms have been referred to as monads, though this term is used more specifically to describe organisms of the genus Monas. The main groups of organisms are bacteria, archaea, protozoa, unicellular algae. Unicellular organisms fall into two categories, prokaryotic organisms and eukaryotic organisms. Unicellular organisms are thought to be the oldest form of life, prokaryotes, most Protista, and some fungi are unicellular. Although some of these live in colonies, they dont exhibit specialization. These organisms live together, and each cell in the colony is the same, however, each individual cell must carry out all life processes to survive. In contrast, even the simplest multicellular organisms have cells that depend on each other to survive, most multicellular organisms have a unicellular life-cycle stage. Gametes, for example, are reproductive unicells for multicellular organisms, additionally, multicellularity appears to have evolved independently many times in the history of life. Some organisms are partially uni- and multicellular, like Dictyostelium discoideum, additionally, unicellular organisms can be multinucleate, like Myxogastria and Plasmodium. Candidatus Magnetoglobus multicellular, related to Deltaproteobacteria, is a multicellular prokaryote and it is neither unicellular, nor a colony. Primitive cells, often referred to as protocells, are the precursors to todays unicellular organisms, the RNA world hypothesis assumes that RNA molecules could form in abiotic conditions, which would require nucleic acids and ribose to be present. Theoretical and experimental findings show that nucleic acids and sugars could have been synthesized in early prebiotic conditions, compartmentalization was necessary for chemical reactions to be more likely as well as to differentiate reactions with the external environment. For example, an early RNA replicator ribozyme may have replicated other replicator ribozymes of different RNA sequences if not kept separate, when amphiphiles like lipids are placed in water, the hydrophobic tails aggregate to form micelles and vesicles, with the hydrophilic ends facing outwards. Primitive cells likely used self-assembling fatty-acid vesicles to separate chemical reactions, because of their simplicity and ability to self-assemble in water, its likely that these simple membranes predated other forms of early biological molecules. Prokaryotes lack membrane-bound organelles, such as mitochondria or a nucleus, instead, most prokaryotes have an irregular region that contains DNA, known as the nucleoid. Most prokaryotes have a single, circular chromosome, which is in contrast to eukaryotes, nutritionally, prokaryotes have the ability to utilize a wide range of organic and inorganic material for use in metabolism, including sulfur, cellulose, ammonia, or nitrite. Prokaryotes as a whole are ubiquitous in the environment and exist in extreme environments as well, bacteria are one of the world’s oldest forms of life, and are found virtually everywhere in nature

Unicellular organism
–
Valonia ventricosa, a species of algae with a diameter that ranges typically from 1 to 4 centimetres (0.39 to 1.57 in) is among the largest unicellular species

16.
Silurian
–
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period,419.2 Mya. As with other periods, the rock beds that define the periods start and end are well identified. The base of the Silurian is set at a major Ordovician-Silurian extinction event when 60% of marine species were wiped out, a significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian, the Silurian system was first identified by British geologist Sir Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick and this naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures. As it was first identified, the Silurian series when traced farther afield quickly came to overlap Sedgwicks Cambrian sequence, however, charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was Gotlandian after the strata of the Baltic island of Gotland, the French geologist Joachim Barrande, building on Murchisons work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages and his interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils. The epoch is named for the town of Llandovery in Carmarthenshire, the Wenlock, which lasted from 433.4 ±1.5 to 427.4 ±2.8 mya, is subdivided into the Sheinwoodian and Homerian ages. It is named after Wenlock Edge in Shropshire, England, during the Wenlock, the oldest known tracheophytes of the genus Cooksonia, appear. The first terrestrial animals also appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ±1.5 to 423 ±2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and it is named for the town of Ludlow in Shropshire, England. The Pridoli, lasting from 423 ±1.5 to 419.2 ±2.8 mya, is the final and it is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a field area. The high sea levels of the Silurian and the flat land resulted in a number of island chains. The southern continents remained united during this period, the melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia, Baltica, and Laurentia drifted together near the equator and this event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway

17.
Flowering plant
–
The flowering plants, also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 416 families, approx. 13,164 known genera and a total of c.295,383 known species, etymologically, angiosperm means a plant that produces seeds within an enclosure, in other words, a fruiting plant. The term angiosperm comes from the Greek composite word meaning enclosed seeds, the ancestors of flowering plants diverged from gymnosperms in the Triassic Period, during the range 245 to 202 million years ago, and the first flowering plants are known from 160 mya. They diversified extensively during the Lower Cretaceous, became widespread by 120 mya, angiosperms differ from other seed plants in several ways, described in the table. These distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants, the amount and complexity of tissue-formation in flowering plants exceeds that of gymnosperms. The vascular bundles of the stem are arranged such that the xylem and phloem form concentric rings, in the dicotyledons, the bundles in the very young stem are arranged in an open ring, separating a central pith from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of meristem or active formative tissue known as cambium, the soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Among the monocotyledons, the bundles are more numerous in the stem and are scattered through the ground tissue. They contain no cambium and once formed the stem increases in diameter only in exceptional cases, the characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, and provide the most trustworthy external characteristics for establishing relationships among angiosperm species, the function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds. The floral apparatus may arise terminally on a shoot or from the axil of a leaf, occasionally, as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. There are two kinds of cells produced by flowers. Microspores, which divide to become pollen grains, are the male cells and are borne in the stamens. The female cells called megaspores, which divide to become the egg cell, are contained in the ovule. The flower may consist only of parts, as in willow. Usually, other structures are present and serve to protect the sporophylls, the individual members of these surrounding structures are known as sepals and petals. The outer series is usually green and leaf-like, and functions to protect the rest of the flower, the inner series is, in general, white or brightly colored, and is more delicate in structure. It functions to attract insect or bird pollinators, attraction is effected by color, scent, and nectar, which may be secreted in some part of the flower

18.
History of Earth
–
The history of Earth concerns the development of the planet Earth from its formation to the present day. Nearly all branches of science have contributed to the understanding of the main events of the Earths past. The age of Earth is approximately one-third of the age of the universe, an immense amount of geological change has occurred in that timespan, accompanied by the emergence of life and its subsequent evolution. Earth formed around 4.54 billion years ago by accretion from the solar nebula, volcanic outgassing probably created the primordial atmosphere and then the ocean, but the atmosphere contained almost no oxygen and so would have been toxic to most modern life including humans. Much of the Earth was molten because of frequent collisions with other bodies which led to extreme volcanism. A giant impact collision with a body named Theia while Earth was in its earliest stage. Over time, the Earth cooled, causing the formation of a solid crust, the geological time scale clock depicts the larger spans of time from the beginning of the Earth as well as a chronology of some definitive events of Earth history. The Archean and Proterozoic eons follow, they produced the abiogenesis of life on Earth, there are microbial mat fossils such as stromatolites found in 3.48 billion-year-old sandstone discovered in Western Australia. According to one of the researchers, If life arose relatively quickly on Earth … then it could be common in the universe, living forms derived from photosynthesis appeared between 3.2 and 2.4 billion years ago and began enriching the atmosphere with oxygen. More than 99 percent of all species, amounting to five billion species. Estimates on the number of Earths current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described. Geological change has been a constant of Earths crust since the time of its formation, species continue to evolve, taking on new forms, splitting into daughter species or going extinct in the process of adapting or dying in response to ever-changing physical environments. The process of plate tectonics continues to play a dominant role in the shaping of Earths oceans and continents, in geochronology, time is generally measured in mya, each unit representing the period of approximately 1,000,000 years in the past. The history of Earth is divided into four great eons, starting 4,540 mya with the formation of the planet, each eon saw the most significant changes in Earths composition, climate and life. Each eon is divided into eras, which in turn are divided into periods. The history of the Earth can be organized according to the geologic time scale. The following four timelines show the time scale

History of Earth
–
Artistic concept of the primordial Earth when it was much hotter and hostile to life
History of Earth
–
An artist's rendering of a protoplanetary disk
History of Earth
–
Geologic map of North America, color-coded by age. The reds and pinks indicate rock from the Archean.
History of Earth
–
Lithifiedstromatolites on the shores of Lake Thetis, Western Australia. Archean stromatolites are the first direct fossil traces of life on Earth.

19.
Age of the Earth
–
The age of the Earth is 4.54 ±0.05 billion years. This dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the ages of the oldest-known terrestrial. Following the development of radiometric age-dating in the early 20th century, the oldest such minerals analyzed to date—small crystals of zircon from the Jack Hills of Western Australia—are at least 4.404 billion years old. Comparing the mass and luminosity of the Sun to those of other stars and it is hypothesised that the accretion of Earth began soon after the formation of the calcium-aluminium-rich inclusions and the meteorites. It is also difficult to determine the age of the oldest rocks on Earth, exposed at the surface. Studies of strata, the layering of rocks and earth, gave naturalists an appreciation that Earth may have been many changes during its existence. These layers often contained fossilized remains of creatures, leading some to interpret a progression of organisms from layer to layer. Nicolas Steno in the 17th century was one of the first naturalists to appreciate the connection between fossil remains and strata and his observations led him to formulate important stratigraphic concepts. In the 1790s, William Smith hypothesized that if two layers of rock at widely differing locations contained similar fossils, then it was plausible that the layers were the same age. William Smiths nephew and student, John Phillips, later calculated by means that Earth was about 96 million years old. In the mid-18th century, the naturalist Mikhail Lomonosov suggested that Earth had been created separately from, and several hundred years before. In 1779 the Comte du Buffon tried to obtain a value for the age of Earth using an experiment, He created a globe that resembled Earth in composition. This led him to estimate that Earth was about 75,000 years old, other naturalists used these hypotheses to construct a history of Earth, though their timelines were inexact as they did not know how long it took to lay down stratigraphic layers. This was a challenge to the view, which saw the history of Earth as static. Many naturalists were influenced by Lyell to become uniformitarians who believed that changes were constant, in 1862, the physicist William Thomson, 1st Baron Kelvin published calculations that fixed the age of Earth at between 20 million and 400 million years. He assumed that Earth had formed as a completely molten object, geologists such as Charles Lyell had trouble accepting such a short age for Earth. For biologists, even 100 million years seemed much too short to be plausible, in Darwins theory of evolution, the process of random heritable variation with cumulative selection requires great durations of time. In a lecture in 1869, Darwins great advocate, Thomas H. Huxley, attacked Thomsons calculations and their values were consistent with Thomsons calculations

Age of the Earth
–
Earth as seen from Apollo 17
Age of the Earth
–
William Thomson (Lord Kelvin)
Age of the Earth
–
Ernest Rutherford in 1908.
Age of the Earth
–
Fragment of the Canyon Diablo iron meteorite.

20.
Origin of water on Earth
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The origin of water on Earth, or the reason that there is clearly more liquid water on Earth than on the other rocky planets of the Solar System, is not completely understood. There exist numerous more or less mutually compatible hypotheses as to how water may have accumulated on Earths surface over the past 4.5 billion years in sufficient quantity to form oceans. Comets, trans-Neptunian objects or water-rich meteoroids from the reaches of the asteroid belt colliding with Earth may have brought water to the worlds oceans. Large enough Planetesimals were heated by the decay of aluminium isotope and this could cause water to rise to the surface. What is however unclear is whether these comets are representative of those from the Kuiper Belt, the water in carbon-rich chondrites point to a similar D/H ratio as oceanic water. Nevertheless, mechanisms have been proposed to suggest that the D/H-ratio of oceanic water may have increased significantly throughout Earths history, such a proposal is consistent with the possibility that a significant amount of the water on Earth was already present during the planets early evolution. Recent measurements of the composition of Moon rocks suggest that Earth was born with its water already present. Investigating lunar samples carried to Earth by the Apollo 15 and 17 missions found a ratio that matched the isotopic ratio in carbonaceous chondrites. The ratio is similar to that found in water on Earth. The findings suggest a common source of water for both objects and this supports a theory that Jupiter temporarily migrated into the inner Solar System, destabilizing the orbits of water-rich carbonaceous chondrites. As a result, some of the bodies could have fallen inwards and become part of the raw material for making Earth, the discovery of water vapor out-gassing from Ceres provides related information on water-ice content of the asteroid belt. Gradual leakage of stored in hydrate minerals of Earths rocks could have formed a portion of its water. Water may also have come from volcanism, water vapor in the atmosphere that originated in volcanic eruptions may have condensed to form rain, a sizeable quantity of water would have been in the material that formed Earth. Water molecules would have escaped Earths gravity more easily when it was less massive during its formation, part of the young planet is theorized to have been disrupted by the impact which created the Moon, which should have caused melting of one or two large areas. Present composition does not match complete melting and it is hard to melt, however, a fair fraction of material should have been vaporized by this impact, creating a rock-vapor atmosphere around the young planet. The rock-vapor would have condensed within two years, leaving behind hot volatiles which probably resulted in a heavy carbon dioxide atmosphere with hydrogen. Liquid water oceans existed despite the temperature of 230°C because of the atmospheric pressure of the heavy CO2 atmosphere. As cooling continued, subduction and dissolving in ocean water removed most CO2 from the atmosphere but levels oscillated wildly as new surface and mantle cycles appeared

Origin of water on Earth
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Water covers about 75% of the Earth's surface

21.
Geological history of oxygen
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Before photosynthesis evolved, Earths atmosphere had no free oxygen. Photosynthetic prokaryotic organisms that produced O2 as a waste product lived long before the first build-up of free oxygen in the atmosphere, the oxygen they produced would have been rapidly removed from the atmosphere by weathering of reducing minerals, most notably iron. This mass rusting led to the deposition of oxide on the ocean floor. Oxygen only began to persist in the atmosphere in small quantities about 50 million years before the start of the Great Oxygenation Event and this mass oxygenation of the atmosphere resulted in rapid buildup of free oxygen. At current rates of production, todays concentration of oxygen could be produced by photosynthetic organisms in 2,000 years.9 billion years ago. The presence of O2 provided life with new opportunities, aerobic metabolism is more efficient than anaerobic pathways, and the presence of oxygen undoubtedly created new possibilities for life to explore. Since the start of the Cambrian period, atmospheric oxygen concentrations have fluctuated between 15% and 35% of atmospheric volume. The maximum of 35% was reached towards the end of the Carboniferous period, whilst human activities, such as the burning of fossil fuels, affect relative carbon dioxide concentrations, their effect on the much larger concentration of oxygen is less significant. But Haldanes essay points out that it would apply to insects. However, the basis for this correlation is not firm. There is no significant correlation between atmospheric oxygen and maximum body size elsewhere in the geological record, ecological constraints can better explain the diminutive size of post-Carboniferous dragonflies - for instance, the appearance of flying competitors such as pterosaurs, birds and bats. The most celebrated link between oxygen and evolution occurs at the end of the last of the Snowball glaciations, where complex life is first found in the fossil record. Significant concentrations of oxygen were just one of the prerequisites for the evolution of complex life, models based on uniformitarian principles suggest that such a concentration was only reached immediately before metazoa first appeared in the fossil record. First breath, Earths billion-year struggle for oxygen New Scientist, #2746,5 February 2010 by Nick Lane, the Mystery of Earths Oxygen New York Times,3 October 2013 by Carl Zimmer

Geological history of oxygen

22.
Ediacaran biota
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The Ediacaran biota consisted of enigmatic tubular and frond-shaped, mostly sessile organisms that lived during the Ediacaran Period. Trace fossils of organisms have been found worldwide, and represent the earliest known complex multicellular organisms. The Ediacaran biota radiated in an event called the Avalon explosion,575 million years ago, the biota largely disappeared with the rapid increase in biodiversity known as the Cambrian explosion. Most of the existing body plans of animals first appeared in the fossil record of the Cambrian rather than the Ediacaran. For macroorganisms, the Cambrian biota appears to have replaced the organisms that dominated the Ediacaran fossil record. Multiple hypotheses exist to explain the disappearance of this biota, including bias, a changing environment. The morphology and habit of some taxa suggest relationships to Porifera or Cnidaria, Kimberella may show a similarity to molluscs, and other organisms have been thought to possess bilateral symmetry, although this is controversial. Most macroscopic fossils are morphologically distinct from later life-forms, they resemble discs, tubes, one palaeontologist proposed a separate kingdom level category Vendozoa in the Linnaean hierarchy for the Ediacaran biota. The concept of Ediacaran Biota is, of course, somewhat artificial as it can not be defined geographically, stratigraphically, taphonomically, the first Ediacaran fossils discovered were the disc-shaped Aspidella terranovica in 1868. Their discoverer, Scottish geologist Alexander Murray, found them useful aids for correlating the age of rocks around Newfoundland, instead, they were interpreted as gas escape structures or inorganic concretions. No similar structures elsewhere in the world were known and the one-sided debate soon fell into obscurity. It was not until the British discovery of the iconic Charnia in 1957 that the pre-Cambrian was seriously considered as containing life. This frond-shaped fossil was found in Englands Charnwood Forest, and due to the geological mapping of the British Geological Survey there was no doubt these fossils sat in Precambrian rocks. All specimens discovered until 1967 were in coarse-grained sandstone that prevented preservation of fine details, poor communication, combined with the difficulty in correlating globally distinct formations, led to a plethora of different names for the biota. Ediacaran and Ediacarian were subsequently applied to the epoch or period of geological time, in March 2004, the International Union of Geological Sciences ended the inconsistency by formally naming the terminal period of the Neoproterozoic after the Australian locality. The term Ediacaran biota and similar has, at times, been used in a geographic, stratigraphic, taphonomic, or biological sense. Microbial mats are areas of sediment stabilised by the presence of colonies of microbes that secrete sticky fluids or otherwise bind the sediment particles. They appear to migrate upwards when covered by a layer of sediment but this is an illusion caused by the colonys growth, individuals do not, themselves

23.
Cambrian explosion
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Lasting for about the next 20–25 million years, it resulted in the divergence of most modern metazoan phyla. Additionally, the event was accompanied by major diversification of other organisms, prior to the Cambrian explosion, most organisms were simple, composed of individual cells occasionally organized into colonies. Over the following 70 to 80 million years, the rate of diversification accelerated by an order of magnitude, almost all present animal phyla appeared during this period. There is strong evidence for species of Cnidaria and Porifera existing in the Ediacaran, bryozoans dont appear in the fossil record until after the Cambrium, in the Lower Ordovician. The Cambrian explosion has generated extensive scientific debate, interpretation is difficult due to a limited supply of evidence, based mainly on an incomplete fossil record and chemical signatures remaining in Cambrian rocks. The first discovered Cambrian fossils were trilobites, described by Edward Lhuyd, nineteenth-century geologists such as Adam Sedgwick and Roderick Murchison used the fossils for dating rock strata, specifically for establishing the Cambrian and Silurian periods. He reasoned that earlier seas had swarmed with living creatures, earlier fossil evidence has since been found. Fossils of more complex cells, from which all animals, plants. Rocks dating from 580 to 543 million years ago contain fossils of the Ediacara biota, organisms so large that they are likely multicelled, the most common organism, Marrella, was clearly an arthropod, but not a member of any known arthropod class. Stephen Jay Goulds popular 1989 account of work, Wonderful Life, brought the matter into the public eye. While differing significantly in details, both Whittington and Gould proposed that all animal phyla had appeared almost simultaneously in a rather short span of geological period. Other analyses, some recent and some dating back to the 1970s. Radiometric dates for much of the Cambrian, obtained by analysis of elements contained within rocks, have only recently become available. Therefore, dates or descriptions of sequences of events should be regarded with some caution until better data become available, fossils of organisms bodies are usually the most informative type of evidence. Fossilization is an event, and most fossils are destroyed by erosion or metamorphism before they can be observed. Hence, the record is very incomplete, increasingly so as earlier times are considered. Despite this, they are adequate to illustrate the broader patterns of lifes history. Also, biases exist in the record, different environments are more favourable to the preservation of different types of organism or parts of organisms

24.
Human
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Modern humans are the only extant members of Hominina tribe, a branch of the tribe Hominini belonging to the family of great apes. Several of these hominins used fire, occupied much of Eurasia and they began to exhibit evidence of behavioral modernity around 50,000 years ago. In several waves of migration, anatomically modern humans ventured out of Africa, the spread of humans and their large and increasing population has had a profound impact on large areas of the environment and millions of native species worldwide. Humans are uniquely adept at utilizing systems of communication for self-expression and the exchange of ideas. Humans create complex structures composed of many cooperating and competing groups, from families. Social interactions between humans have established a wide variety of values, social norms, and rituals. These human societies subsequently expanded in size, establishing various forms of government, religion, today the global human population is estimated by the United Nations to be near 7.5 billion. In common usage, the word generally refers to the only extant species of the genus Homo—anatomically and behaviorally modern Homo sapiens. In scientific terms, the meanings of hominid and hominin have changed during the recent decades with advances in the discovery, there is also a distinction between anatomically modern humans and Archaic Homo sapiens, the earliest fossil members of the species. The English adjective human is a Middle English loanword from Old French humain, ultimately from Latin hūmānus, the words use as a noun dates to the 16th century. The native English term man can refer to the species generally, the species binomial Homo sapiens was coined by Carl Linnaeus in his 18th century work Systema Naturae. The generic name Homo is a learned 18th century derivation from Latin homō man, the species-name sapiens means wise or sapient. Note that the Latin word homo refers to humans of either gender, the genus Homo evolved and diverged from other hominins in Africa, after the human clade split from the chimpanzee lineage of the hominids branch of the primates. The closest living relatives of humans are chimpanzees and gorillas, with the sequencing of both the human and chimpanzee genome, current estimates of similarity between human and chimpanzee DNA sequences range between 95% and 99%. The gibbons and orangutans were the first groups to split from the leading to the humans. The splitting date between human and chimpanzee lineages is placed around 4–8 million years ago during the late Miocene epoch, during this split, chromosome 2 was formed from two other chromosomes, leaving humans with only 23 pairs of chromosomes, compared to 24 for the other apes. There is little evidence for the divergence of the gorilla, chimpanzee. Each of these species has been argued to be an ancestor of later hominins

25.
Phanerozoic
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The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 541 million years to the present, and began with the Cambrian Period when diverse hard-shelled animals first appeared. Its name was derived from the Ancient Greek words φανερός and ζωή, meaning life, since it was once believed that life began in the Cambrian. The time before the Phanerozoic, called the Precambrian supereon, is now divided into the Hadean, Archaean, land plant life appeared in the early Phanerozoic eon. During this time span, tectonic forces caused the continents to move and eventually collect into a landmass known as Pangaea. The Proterozoic-Phanerozoic boundary is at 541 million years ago, the three different dividing points are within a few million years of each other. The Phanerozoic is divided into three eras, the Paleozoic, Mesozoic, and Cenozoic, which are subdivided into 12 periods. The Paleozoic features the rise of fish, amphibians and reptiles, the Mesozoic is ruled by the reptiles, and features the evolution of mammals, birds and more famously, dinosaurs. The Cenozoic is the time of the mammals, and more recently, the Paleozoic is a time in Earths history when complex life forms evolved, took their first breath of oxygen on dry land, and when the forerunners of all life on Earth began to diversify. There are six periods in the Paleozoic era, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, the Cambrian is the first period of the Paleozoic Era and starts from 541 to 485 million years ago. The Cambrian sparked a rapid expansion in evolution in an event known as the Cambrian Explosion during which the greatest number of creatures evolved in a period in the history of Earth. Plants like algae evolved, and the fauna was dominated by armored arthropods, almost all marine phyla evolved in this period. During this time, the super-continent Pannotia began to break up, the Ordovician spans from 485 million years to 440 million years. The Ordovician was a time in Earths history in many species still prevalent today evolved, such as primitive fish, cephalopods. The most common forms of life, however, were trilobites, snails, more importantly, the first arthropods crept ashore to colonize Gondwana, a continent empty of animal life. By the end of the Ordovican, Gondwana had moved from the equator to the South Pole, the glaciation of Gondwana resulted in a major drop in sea level, killing off all life that had established along its coast. Glaciation caused a snowball Earth, leading to the Ordovician-Silurian extinction, during which 60% of marine invertebrates and this is considered the first mass extinction and the second deadliest in the history of Earth. The Silurian spans from 440 million years to 415 million years, fully terrestrial life evolved, which included early arachnids, fungi, and centipedes

26.
Proterozoic
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The Proterozoic is a geological eon representing the time just before the proliferation of complex life on Earth. The name Proterozoic comes from Greek and means life, the Greek root protero-, means former, earlier and zoic-, means animal. The Proterozoic Eon extended from 2500 Ma to 541 Ma, and is the most recent part of the Precambrian Supereon and it is subdivided into three geologic eras, the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic. The geologic record of the Proterozoic Eon is more complete than that for the preceding Archean Eon, studies of these rocks have shown that the eon continued the massive continental accretion that had begun late in the Archean Eon. The Proterozoic Eon also featured the first definitive supercontinent cycles and wholly modern mountain building activity, there is evidence that the first known glaciations occurred during the Proterozoic. One of the most important events of the Proterozoic was the accumulation of oxygen in the Earths atmosphere, until roughly 2.3 billion years ago, oxygen was probably only 1% to 2% of its current level. The Banded iron formations, which provide most of the iron ore, are one mark of that mineral sink process. Their accumulation ceased after 1.9 billion years ago, after the iron in the oceans had all been oxidized, red beds, which are colored by hematite, indicate an increase in atmospheric oxygen 2 billion years ago. Such massive iron oxide formations are not found in older rocks, the Proterozoic Eon was a very tectonically active period in the Earth’s history. The late Archean Eon to Early Proterozoic Eon corresponds to a period of increasing crustal recycling, suggesting subduction, evidence for this increased subduction activity comes from the abundance of old granites originating mostly after 2.6 Ga. The appearance of eclogites, which metamorphic rocks created by pressure, are explained using a model that incorporates subduction. As a result of remelting of basaltic oceanic crust due to subduction, the long-term tectonic stability of those cratons is why we find continental crust ranging up to a few billion years in age. It is believed that 43% of modern continental crust was formed in the Proterozoic, 39% formed in the Archean, studies by Condie 2000 and Rino et al.2004 suggest that crust production happened episodically. By isotopically calculating the ages of Proterozoic granitoids it was determined there were several episodes of rapid increase in continental crust production. The reason for these pulses is unknown, but they seemed to have decreased in magnitude after every period, evidence of collision and rifting between continents raises the question as to what exactly were the movements of the Archean cratons composing Proterozoic continents. Paleomagnetic and geochronological dating mechanisms have allowed the deciphering of Precambrian Supereon tectonics and it is known that tectonic processes of the Proterozoic Eon resemble greatly the evidence of tectonic activity, such as orogenic belts or ophiolite complexes, we see today. Hence, most geologists would conclude that the Earth was active at that time and it is also commonly accepted that during the Precambrian, the Earth went through several supercontinent breakup and rebuilding cycles. In the late Proterozoic, the dominant supercontinent was Rodinia and it consisted of a series of continents attached to a central craton that forms the core of the North American Continent called Laurentia

27.
Cryogenian
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The Cryogenian is a geologic period that lasted from 720 to 635 million years ago. It forms the geologic period of the Neoproterozoic Era, preceded by the Tonian Period. The Sturtian and Marinoan glaciations during the Cryogenian period, which are the greatest ice ages known to have occurred on Earth and these events are the subject of much scientific controversy. The main debate contests whether these glaciations covered the planet or if a band of open sea survived near the equator. The Cryogenian period was ratified in 1990 by the International Commission on Stratigraphy, in contrast to most other time periods, the beginning of the Cryogenian is not linked to a globally observable and documented event. Instead, the base of the period is defined by a fixed age, that was set at 850 million years, until 2015. This is problematic as estimates of rock ages are variable and are subject to laboratory error, for instance, the time scale of the Cambrian Period is not reckoned by rock younger than a given age, but by the appearance of the worldwide Treptichnus pedum diagnostic trace fossil assemblages. This means that rocks can be recognized as Cambrian when examined in the field, currently, there is no consensus on what global event is a suitable candidate to mark the start of the Cryogenian Period, but a global glaciation would be a likely candidate. The name of the geologic period refers to the very cold climate of the Cryogenian. Characteristic glacial deposits indicate that Earth suffered the most severe ice ages in its history during this period, according to Eyles and Young, Late Proterozoic glaciogenic deposits are known from all the continents. They provide evidence of the most widespread and long-ranging glaciation on Earth, several glacial periods are evident, interspersed with periods of relatively warm climate, with glaciers reaching sea level in low paleolatitudes. Glaciers extended and contracted in a series of pulses, possibly reaching as far as the equator. The Cryogenian is generally considered to be divisible into at least two major worldwide glaciations, the Sturtian glaciation persisted from 720 to 660 million years ago, and the Marinoan glaciation which ended approximately 635 Ma, at the end of the Cryogenian. Before the start of the Cryogenian, around 750 Ma, the cratons that made up the supercontinent Rodinia started to rift apart, the superocean Mirovia began to close while the superocean Panthalassa began to form. The cratons later assembled into another supercontinent called Pannotia, in the Ediacaran, Eyles and Young state, Most Neoproterozoic glacial deposits accumulated as glacially influenced marine strata along rifted continental margins or interiors. Worldwide deposition of dolomite might have reduced carbon dioxide. The break up along the margins of Laurentia at about 750 Ma occurs at about the time as the deposition of the Rapitan Group in North America. A similar period of rifting at about 650 Ma occurred with the deposition of the Ice Brook Formation in North America, the Sturtian and Marinoan are local divisions within the Adelaide Rift Complex

Cryogenian

28.
Timeline of glaciation
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There have been five known ice ages in the Earths history, with the Earth experiencing the Quaternary Ice Age during the present time. Within ice ages, there exist periods of more severe conditions and more temperate referred to as glacial periods and interglacial periods. Based on climate proxies, paleoclimatologists study the different climate states originating from glaciation, however, this hypothesis is still controversial, though is growing in popularity among researchers as evidence in its favor has mounted. A minor series of glaciations occurred from 460 Ma to 430 Ma, there were extensive glaciations from 350 to 250 Ma. The current ice age, called the Quaternary glaciation, has more or less extensive glaciation on 40,000. Originally, the glacial and interglacial periods of the Quaternary Ice Age were named after characteristic geological features, and it is now more common for researchers to refer to the periods by their marine isotopic stage number. The marine record preserves all the past glaciations, the evidence is less complete because successive glaciations may wipe out evidence of their predecessors. Ice cores from continental ice accumulations also provide a complete record, pollen data from lakes and bogs as well as loess profiles provided important land-based correlation data. The names system has not been filled out since the technical discussion moved to using marine isotopic stage numbers. Land-based evidence works acceptably well back as far as MIS6, hence, the names system is incomplete and the land-based identifications of ice ages previous to that are somewhat conjectural. Nonetheless, land based data is useful in discussing landforms. The last glacial and interglacial periods of the Quaternary are named, from most recent to most distant, dates shown are in thousand years before present. Older periods of the Quaternary **Table data is based on Gibbard Figure 22.1, Ice cores are used to obtain a high resolution record of recent glaciation. It confirms the chronology of the marine isotopic stages, Ice core data shows that the last 400,000 years have consisted of short interglacials about as warm as the present alternated with much longer glacials substantially colder than present. Regional Glaciation of Kansas and Nebraska, work Group on Geospatial Analysis of Glaciated Environments. Pre-Wisconsin Glaciation of Central North America, Emporia KA, INQUA Commission on Glaciation, Emporia State University. Archived from the original on May 13,2008, global correlation tables for the Quaternary. Cambridge UK, Department of Geography, University of Cambridge, Gibbard, P. L. Boreham, S. Cohen, K. M

Timeline of glaciation
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Showing the major glaciations (Ice Ages) in the context of Earth's entire existence.
Timeline of glaciation
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500 million year record shows current and previous two major glacial periods

29.
Roderick Murchison
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Roderick Impey Murchison, 1st Baronet KCB DCL FRS FRSE FLS PRGS PBA MRIA was a Scottish geologist who first described and investigated the Silurian system. Murchison was born at Tarradale House, Muir of Ord, Ross-shire, the son of Kenneth Murchison. His wealthy father died in 1796, when Roderick was 4 years old, and he was sent to Durham School 3 years later, in 1808 he landed with Wellesley in Galicia, and was present at the actions of Roliça and Vimeiro. Subsequently under Sir John Moore, he took part in the retreat to Corunna, after eight years of service Murchison left the army, and married Charlotte Hugonin, the only daughter of General Hugonin, of Nursted House, Hampshire. Murchison and his wife spent two years in mainland Europe, particularly in Italy and they then settled in Barnard Castle, County Durham, England in 1818 where Murchison made the acquaintance of Sir Humphry Davy. Davy urged Murchison to turn his energy to science, after hearing that he wasted his time riding to hounds, Murchison became fascinated by the young science of geology and joined the Geological Society of London, soon becoming one of its most active members. His colleagues there included Adam Sedgwick, William Conybeare, William Buckland, William Fitton, Charles Lyell, turning his attention to Continental geology, he and Lyell explored the volcanic region of Auvergne, parts of southern France, northern Italy, Tyrol and Switzerland. A little later, with Sedgwick as his companion, Murchison attacked the problem of the geological structure of the Alps. Their joint paper giving the results of their study is a classic in the literature of Alpine geology. In 1831 he went to the border of England and Wales and these researches, together with descriptions of the coalfields and overlying formations in South Wales and the English border counties, were embodied in The Silurian System. The establishment of the Silurian system was followed by that of the Devonian system and he was accompanied by Edouard de Verneuil and Count Alexander von Keyserling, in conjunction with whom he produced a work on Russia and the Ural Mountains. The publication of this monograph in 1845 completes the first and most active half of Murchison’s scientific career and he was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1840. In 1846 he was knighted, and in the year he presided over the meeting of the British Association at Southampton. He served on the Royal Commission on the British Museum, in 1845, whilst visiting Carclew in Cornwall, he met several Cornish miners who were going to Australia. Believing that there may have been gold there he asked them to send back likely samples and they did this and thus Murchison knew of the existence of gold in Australia before Edward Hargraves discovery. In 1857, Murchison was elected a member of the American Antiquarian Society, in 1863, he was made a KCB, and three years later was created a baronet. There was hardly a foreign scientific society of note without his name among its honorary members, the French Academy of Sciences awarded him the prix Cuvier, and elected him one of its eight foreign members in succession to Michael Faraday. In 1855, he was elected a member of the Royal Swedish Academy of Sciences

30.
Stratum
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In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers. The stratum is the unit in a stratigraphic column and forms the basis of the study of stratigraphy. Each layer is one of a number of parallel layers that lie one upon another. They may extend over hundreds of thousands of kilometers of the Earths surface. Strata are typically seen as bands of different colored or differently structured material exposed in cliffs, road cuts, quarries, individual bands may vary in thickness from a few millimeters to a kilometer or more. Each band represents a mode of deposition, river silt, beach sand, coal swamp, sand dune, lava bed. Geologists study rock strata and categorize them by the material of beds, each distinct layer is typically assigned to the name of sheet, usually based on a town, river, mountain, or region where the formation is exposed and available for study. For example, the Burgess Shale is an exposure of dark, occasionally fossiliferous. Slight distinctions in material in a formation may be described as members, formations are collected into groups while groups may be collected into supergroups. Archaeological horizon Geologic formation Geologic map Geologic unit Law of superposition Bed GeoWhen Database

31.
Wales
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Wales is a country that is part of the United Kingdom and the island of Great Britain. It is bordered by England to the east, the Irish Sea to the north and west, and it had a population in 2011 of 3,063,456 and has a total area of 20,779 km2. Wales has over 1,680 miles of coastline and is mountainous, with its higher peaks in the north and central areas, including Snowdon. The country lies within the temperate zone and has a changeable. Welsh national identity emerged among the Celtic Britons after the Roman withdrawal from Britain in the 5th century, Llywelyn ap Gruffudds death in 1282 marked the completion of Edward I of Englands conquest of Wales, though Owain Glyndŵr briefly restored independence to Wales in the early 15th century. The whole of Wales was annexed by England and incorporated within the English legal system under the Laws in Wales Acts 1535–1542, distinctive Welsh politics developed in the 19th century. Welsh Liberalism, exemplified in the early 20th century by Lloyd George, was displaced by the growth of socialism, Welsh national feeling grew over the century, Plaid Cymru was formed in 1925 and the Welsh Language Society in 1962. Established under the Government of Wales Act 1998, the National Assembly for Wales holds responsibility for a range of devolved policy matters, two-thirds of the population live in south Wales, mainly in and around Cardiff, Swansea and Newport, and in the nearby valleys. Now that the countrys traditional extractive and heavy industries have gone or are in decline, Wales economy depends on the sector, light and service industries. Wales 2010 gross value added was £45.5 billion, over 560,000 Welsh language speakers live in Wales, and the language is spoken by a majority of the population in parts of the north and west. From the late 19th century onwards, Wales acquired its popular image as the land of song, Rugby union is seen as a symbol of Welsh identity and an expression of national consciousness. The Old English-speaking Anglo-Saxons came to use the term Wælisc when referring to the Celtic Britons in particular, the modern names for some Continental European lands and peoples have a similar etymology. The modern Welsh name for themselves is Cymry, and Cymru is the Welsh name for Wales and these words are descended from the Brythonic word combrogi, meaning fellow-countrymen. The use of the word Cymry as a self-designation derives from the location in the post-Roman Era of the Welsh people in modern Wales as well as in northern England and southern Scotland. It emphasised that the Welsh in modern Wales and in the Hen Ogledd were one people, in particular, the term was not applied to the Cornish or the Breton peoples, who are of similar heritage, culture, and language to the Welsh. The word came into use as a self-description probably before the 7th century and it is attested in a praise poem to Cadwallon ap Cadfan c. 633. Thereafter Cymry prevailed as a reference to the Welsh, until c.1560 the word was spelt Kymry or Cymry, regardless of whether it referred to the people or their homeland. The Latinised forms of names, Cambrian, Cambric and Cambria, survive as lesser-used alternative names for Wales, Welsh

32.
Celts
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The history of pre-Celtic Europe remains very uncertain. According to one theory, the root of the Celtic languages, the Proto-Celtic language, arose in the Late Bronze Age Urnfield culture of Central Europe. Thus this area is called the Celtic homeland. The earliest undisputed examples of a Celtic language are the Lepontic inscriptions beginning in the 6th century BC. Continental Celtic languages are attested almost exclusively through inscriptions and place-names, Insular Celtic languages are attested beginning around the 4th century in Ogham inscriptions, although it was clearly being spoken much earlier. Celtic literary tradition begins with Old Irish texts around the 8th century, coherent texts of Early Irish literature, such as the Táin Bó Cúailnge, survive in 12th century recensions. Between the 5th and 8th centuries, the Celtic-speaking communities in these Atlantic regions emerged as a cohesive cultural entity. They had a linguistic, religious and artistic heritage that distinguished them from the culture of the surrounding polities. By the 6th century, however, the Continental Celtic languages were no longer in wide use, Insular Celtic culture diversified into that of the Gaels and the Celtic Britons of the medieval and modern periods. A modern Celtic identity was constructed as part of the Romanticist Celtic Revival in Great Britain, Ireland, today, Irish, Scottish Gaelic, Welsh, and Breton are still spoken in parts of their historical territories, and Cornish and Manx are undergoing a revival. The first recorded use of the name of Celts – as Κελτοί – to refer to a group was by Hecataeus of Miletus, the Greek geographer, in 517 BC. In the fifth century BC Herodotus referred to Keltoi living around the head of the Danube, the etymology of the term Keltoi is unclear. Possible roots include Indo-European *kʲel ‘to hide’, IE *kʲel ‘to heat’ or *kel ‘to impel’, several authors have supposed it to be Celtic in origin, while others view it as a name coined by Greeks. Linguist Patrizia De Bernardo Stempel falls in the group. Yet he reports Celtic peoples in Iberia, and also uses the ethnic names Celtiberi and Celtici for peoples there, as distinct from Lusitani, pliny the Elder cited the use of Celtici in Lusitania as a tribal surname, which epigraphic findings have confirmed. Latin Gallus might stem from a Celtic ethnic or tribal name originally and its root may be the Proto-Celtic *galno, meaning “power, strength”, hence Old Irish gal “boldness, ferocity” and Welsh gallu “to be able, power”. The tribal names of Gallaeci and the Greek Γαλάται most probably have the same origin, the suffix -atai might be an Ancient Greek inflection. Proto-Germanic *walha is derived ultimately from the name of the Volcae and this means that English Gaul, despite its superficial similarity, is not actually derived from Latin Gallia, though it does refer to the same ancient region

33.
Silures
–
The Silures were a powerful and warlike tribe or tribal confederation of ancient Britain, occupying what is now south east Wales and perhaps some adjoining areas. They were bordered to the north by the Ordovices, to the east by the Dobunni, according to Tacituss biography of Agricola, the Silures usually had a dark complexion and curly hair. Due to their appearance, Tacitus believed they had crossed over from Spain at an earlier date, jordanes, in his Origins and Deeds of the Goths, describes the Silures. The Silures have swarthy features and are born with curly black hair. They are like the Gauls or the Spaniards, the Latin word Silures is of Celtic origin, perhaps derived from the Common Celtic root *sīlo-, seed. Words derived from this root in Celtic languages are used to mean blood-stock, descendants, lineage, offspring, Silures might therefore mean Kindred, Stock, perhaps referring to a tribal belief in a descent from an originating ancestor. Patrizia de Bernardo Stempel hypothesises that the Silures were originally silo-riks, the first attack on the Welsh tribes was by the legate Publius Ostorius Scapula about AD48. Ostorius first attacked the Deceangli in the north-east of what is now Wales and he then spent several years campaigning against the Silures and the Ordovices. Their resistance was led by Caratacus, who had fled from the south-east when it was conquered by the Romans and he first led the Silures, then moved to the territory of the Ordovices, where he was defeated by Ostorius in AD51. The Silures were not subdued, however, and waged guerrilla warfare against the Roman forces. Ostorius had announced that they posed such a danger that they should be exterminated or transplanted. They also took Roman prisoners as hostages and distributed them amongst their neighbouring tribes in order to them together. Ostorius died with the Silures still unconquered and, after his death, the Roman Tacitus wrote of the Silures, non atrocitate, non clementia mutabatur– the tribe was changed neither by cruelty nor by clemency. To aid the Roman administration in keeping down local opposition, a fortress was planted in the midst of tribal territory. The town of Venta Silurum was established in AD75 and it became a Romanized town, not unlike Calleva Atrebatum, but smaller. An inscription shows that, under the Roman Empire, it was the capital of the Silures and its massive Roman walls still survive, and excavations have revealed a forum, a temple, baths, amphitheatre, shops, and many comfortable houses with mosaic floors, etc. In the late 1st and early 2nd centuries, the Silures were given some nominal independence and responsibility for local administration. As was standard practice, as revealed by inscriptions, the Romans matched their deities with local Silurian ones, and the local deity Ocelus was identified with Mars, the Roman god of war

Silures
–
Tribes of Wales at the time of the Roman invasion. The modern Welsh border is also shown, for reference purposes.

34.
Geological time scale
–
The table of geologic time spans, presented here, agrees with the nomenclature, dates and standard color codes set forth by the International Commission on Stratigraphy. Evidence from radiometric dating indicates that Earth is about 4.54 billion years old, the geology or deep time of Earth’s past has been organized into various units according to events which took place in each period. Older time spans, which predate the reliable record, are defined by their absolute age. Some other planets and moons within the Solar System have sufficiently rigid structures to have preserved records of their own histories, for example, Venus, Mars, dominantly fluid planets, such as the gas giants, do not preserve their history in a comparable manner. Apart from the Late Heavy Bombardment, events on other planets probably had little influence on the Earth. Construction of a scale that links the planets is, therefore, of only limited relevance to the Earths time scale. The existence, timing, and terrestrial effects of the Late Heavy Bombardment is still debated, the largest defined unit of time is the supereon, composed of eons. Eons are divided into eras, which are in turn divided into periods, epochs, the terms eonothem, erathem, system, series, and stage are used to refer to the layers of rock that correspond to these periods of geologic time in Earths history. Geologists qualify these units as early, mid, and late when referring to time, and lower, middle, for example, the lower Jurassic Series in chronostratigraphy corresponds to the early Jurassic Epoch in geochronology. The adjectives are capitalized when the subdivision is formally recognized, and lower case when not, thus early Miocene but Early Jurassic. Geologic units from the time but different parts of the world often look different and contain different fossils. For example, in North America the Lower Cambrian is called the Waucoban series that is subdivided into zones based on succession of trilobites. In East Asia and Siberia, the unit is split into Alexian, Atdabanian. A key aspect of the work of the International Commission on Stratigraphy is to reconcile this conflicting terminology, the term Anthropocene is used informally by popular culture and a growing number of scientists to describe the current epoch in which we are living. The term was coined by Paul Crutzen and Eugene Stoermer in 2000 to describe the current time, others say that humans have not even started to leave their biggest impact on Earth, and therefore the Anthropocene hasnt even started yet. Whatever the case, the ICS has not officially approved the term, leonardo da Vinci concurred with Aristotles interpretation that fossils represented the remains of ancient life. The 11th-century Persian geologist Avicenna and the 13th-century Dominican bishop Albertus Magnus extended Aristotles explanation into a theory of a petrifying fluid. Avicenna also first proposed one of the principles underlying geologic time scales, the Chinese naturalist Shen Kuo also recognized the concept of deep time

Geological time scale
–
Key concepts
Geological time scale

35.
Charles Lapworth
–
Prof Charles Lapworth, FRS|LLD, FGS was an English geologist who pioneered faunal analysis using index fossils and identified the Ordovician period. Charles Lapworth was born at Faringdon in Berkshire the son of James Lapworth and he was trained as a teacher at the Culham Diocesan Training College near Abingdon, Oxfordshire. He moved to the Scottish border region, where he investigated the previously little-known fossil fauna of the area, there in 1869 he married Janet, daughter of Galashiels schoolmaster Walter Sanderson and stayed in the area. He completed this research in the Southern Uplands while employed as a schoolmaster for 11 years at the Episcopal Church school. This proposal resolved a long running controversy which began when Roderick Murchison, Lapworth received numerous awards for his research work, while for teaching he used the English Midlands as a setting for demonstrating the fieldwork techniques he had pioneered in his own research. Later Peach and Horne were dispatched to the area and their monumental memoir proved Lapworth correct, in the English Midlands his research involved important work in Shropshire and the demonstration that Cambrian rocks underlay the Carboniferous rocks between Nuneaton and Atherstone. He died on 13 March 1920 and is buried in Lodge Hill Cemetery near Birmingham and he married Janet Sanderson in 1869. His son Arthur Lapworth became a renowned chemist and his son Herbert a civil engineer, engineering geologist, stratigrapher, Lapworth received many awards for his work and contributions to geology. In June 1888 he was elected a Fellow of the Royal Society, in 1899, he received the highest award of the Geological Society of London, the Wollaston Medal, in recognition of his outstanding work in the Southern Uplands, and Northwest Highlands of Scotland. There years later, in February 1902, he was elected President of the Geological Society for the years 1902-1904, the glacial Lake Lapworth, was named for him by Leonard Johnston Wills in recognition of his original suggestion of its existence in 1898. Aberdeen University awarded him a doctorate in 1884 and Glasgow University in 1912. In 1916 he was elected an Honorary Fellow of the Royal Society of Edinburgh, papers relating to Charles Lapworth can be found at the University of Birmingham Special Collections. The University of Birmingham also maintains the Lapworth Museum within the Aston Webb building on the main Edgbaston campus, the Lapworth Archive, housed in the museum, contains a remarkably complete record of all areas of his research work and teaching. Eminent Living Geologists, Professor Charles Lapworth, Geological Magazine, New Series, Decade IV

36.
Myr
–
The Malaysian ringgit is the currency of Malaysia. It is divided into 100 sen, the ringgit is issued by the Bank Negara Malaysia. In modern usage ringgit is used almost solely for the currency, to differentiate between the three currencies, the Malaysian currency is referred to as Ringgit Malaysia, hence the official abbreviation and currency symbol RM. Internationally, the ISO4217 currency code for Malaysian ringgit is MYR, the Malay names ringgit and sen were officially adopted as the sole official names in August 1975. Previously they had been known officially as dollars and cents in English and ringgit and sen in Malay, in the northern states of Peninsular Malaysia, denominations of 10 sen are called kupang in Malay, e. g.50 sen is 5 kupang. On 12 June 1967, the Malaysian dollar, issued by the new bank, Bank Negara Malaysia, replaced the Malaya. The new currency retained all denominations of its predecessor except the $10,000 denomination, and also brought over the colour schemes of the old dollar. In November 1967, five months after the introduction of the Malaysian dollar and this ended on 8 May 1973, when the Malaysian government withdrew from the agreement. The Monetary Authority of Singapore and the Brunei Currency and Monetary Board still maintain the interchangeability of their two currencies, as of 2009, in 1993, the currency symbol RM was introduced to replace the use of the dollar sign $. US$130 and RM1,000 worth of US$260. Despite these measures, the ringgit lost 50% of its value against the US dollar between 1997 and 1998, and suffered general depreciation against other currencies between December 2001 and January 2005. As of 4 September 2008, the ringgit has yet to regain its value circa 2001 against the Singapore dollar, the euro, the Australian dollar, and the British pound. On 21 July 2005, Bank Negara announced the end of the peg to the US dollar immediately after Chinas announcement of the end of the peg to the US dollar. According to Bank Negara, Malaysia allows the ringgit to operate in a float against several major currencies. Following the end of the peg, the ringgit appreciated to as high as 3.16 to the US dollar in April 2008. The ringgit had also enjoyed a period of appreciation against the Hong Kong dollar, the initial stability of the ringgit in the late-2000s had led to considerations to reintroduce the currency to foreign trading. As a result, the US dollar appreciated significantly to close at 3.43 to the MYR as of 4 September 2008, while other major currencies, including the renminbi and Hong Kong dollar, followed suit. The ringgit spiked at 3.73 to the US dollar by March 2009, before recovering to 3.00 to the US dollar by mid-2011. The first series of sen coins were introduced in 1967 in denominations of 1 sen,5 sen,10 sen,20 sen,50 sen, followed by the introduction of the 1 ringgit coin in 1971

Myr
–
The Malaysian ringgit third series coinage and fourth series banknote designs announced in 2011 by Bank Negara Malaysia.

37.
Llandovery
–
Llandovery is a community and market town in Carmarthenshire, Wales, lying on the River Tywi and the A40/A483 roads. The town is served by Llandovery railway station, where there is a park and ride to Llanelli, Llandovery — a corruption of Llanymddyfri, meaning Llan ymlith y dyfroedd — owes its name to its position between the River Tywi and the Afon Brân just upstream of their confluence. A smaller watercourse, the Bawddwr, runs through and under the town, Llandovery is twinned with Pluguffan in Brittany, France. The Roman fort at Llanfair Hill to the northeast of the town around was known to the Romans as Alabum. It was built around AD50 to 60 as part of their strategy for the conquest of Wales, a Roman road heads across Mynydd Bach Trecastell to the southeast of Llandovery bound for the fort of Brecon Gaer. Another heads down the Towy valley for Carmarthen whilst a third makes for the goldmines at Dolaucothi, the castle was used by King Henry IV while on a sortie into Wales when he executed Llywelyn ap Gruffydd Fychan in the marketplace. It was later attacked by the forces of Owain Glyndŵr in 1403, a 16-foot high stainless steel statue to Llywelyn ap Gruffydd Fychan was unveiled in 2001 on the north side of Llandovery Castle, overlooking the place of his execution six hundred years earlier. He had led the army of King Henry IV on a wild goose chase under the pretence of leading them to a rebel camp. The statue won a competition to choose a suitable design. It was funded by the National Lottery and the Arts Council of Wales, the Physicians of Myddfai practised in the area. Llandovery is also the place one of the first independent Welsh banks. The building is part of the Kings Head inn which was the home of The Bank of the Black Ox, also in the town are a charity-run theatre, a heritage centre and Llandovery College. A tourist information and heritage centre is situated in the heart of the town, the Llandovery Epoch is the earliest in the Silurian Period of geological time. In a small place in the centre of Llandovery is Llandovery Town Hall by the architect Richard Kyke Penson. There is a courtroom over a market, in an Italianate style. The building has two storeys with open arcades, at the rear are police cells with iron grilles and entry to the courtroom under a clock tower. Many visitors use Llandovery as a base for the western part of the Brecon Beacons National Park which lies immediately to the south of the town. For others it is a stop en route to Pembrokeshire and West Wales, large numbers of motorcyclists congregate, particularly at weekends, in the West End cafe on Broad Street, part of the A40

38.
Carmarthenshire
–
Carmarthenshire is a unitary authority in the south-west of Wales and is the largest of the thirteen historic counties of Wales. The three largest towns are Llanelli, Carmarthen and Ammanford, Carmarthen is the county town and administrative centre of Carmarthenshire, but the most populous settlement is Llanelli. Carmarthenshire has been inhabited since prehistoric times, the town of Carmarthen was founded by the Romans, and the region was part of the Principality of Deheubarth during the High Middle Ages. It saw turbulent times during the invasion by the Normans in the 12th and 13h centuries before it was subjugated, along other parts of Wales. There was further unrest in the early 15th century when the Welsh rebelled under Owain Glyndŵr, Carmarthenshire is mainly an agricultural county, apart from the southeastern part which at one time was heavily industrialised with coal mining, steel-making and tin-plating. In the north of the county the woollen industry was important in the 18th century. Nowadays the economy of the county depends on agriculture, forestry, fishing, with the decline in its industrial base and the low profitability of the livestock sector, Carmarthenshire is economically one of the worst-performing regions in the United Kingdom. Although Carmarthenshire is less frequented as a tourist destination than some other counties in Wales, further west are the sandy beaches at Llansteffan and Pendine, and Dylan Thomas boathouse at Laugharne. Further inland there are a number of castles, hillforts. Humans have been living in Carmarthenshire since at least 40,000 years ago as evidenced by stone tools found in Coygan Cave, near Laugharne. The Romans established two forts in South Wales, one at Caerwent to control the southeast of the country, the fort at Carmarthen dates from around 75 AD, and there is a Roman amphitheatre nearby, so this probably makes Carmarthen the oldest continually occupied town in Wales. Carmarthenshire has its roots in the region formerly known as Ystrad Tywi and part of the Principality of Deheubarth during the High Middle Ages. After the Normans had subjugated England they tried to subdue Wales, Carmarthenshire was disputed between the Normans and the Welsh lords and many of the castles built around this time, first of wood and then stone, changed hands several times. Following the Conquest of Wales by Edward I, the region was reorganized by the Statute of Rhuddlan in 1284 into Carmarthenshire. Edward I made Carmarthen the capital of new county, establishing his courts of chancery and his exchequer there. The Normans transformed Carmarthen into a trading port, the only staple port in Wales. Merchants imported food and French wines and exported wool, pelts, leather, lead, Carmarthen was particularly susceptible to plague as it was brought in by flea-infested rats on board ships from southern France. In 1405, Owain Glyndŵr captured Carmarthen Castle and several other strongholds in the neighbourhood, however, when his support dwindled, the principal men of the county returned their allegiance to King Henry V

39.
Shropshire, England
–
Shropshire Council was created in 2009, a unitary authority taking over from the previous county council and five district councils. The borough of Telford and Wrekin has been a unitary authority since 1998. The county has many towns, including Whitchurch in the north, Newport north-east of Telford. The Ironbridge Gorge area is a UNESCO World Heritage Site, covering Ironbridge, Coalbrookdale, there are other historic industrial sites in the county, such as at Shrewsbury, Broseley, Snailbeach and Highley, as well as the Shropshire Union Canal. The Shropshire Hills Area of Outstanding Natural Beauty covers about a quarter of the county, Shropshire is one of Englands most rural and sparsely populated counties, with a population density of 136/km2. The Wrekin is one of the most famous landmarks in the county, though the highest hills are the Clee Hills, Stiperstones. Wenlock Edge is another significant geographical and geological landmark, the River Severn, Great Britains longest river, runs through the county, exiting into Worcestershire via the Severn Valley. Shropshire is landlocked and with an area of 3,487 square kilometres is Englands largest inland county, the county flower is the round-leaved sundew. The area was part of the lands of the Cornovii. This was a tribal Celtic iron age kingdom and their capital in pre-Roman times was probably a hill fort on the Wrekin. Ptolemys 2nd century Geography names one of their towns as being Viroconium Cornoviorum, after the Roman occupation of Britain ended in the 5th century, the Shropshire area was in the eastern part of the Welsh Kingdom of Powys, known in Welsh poetry as the Paradise of Powys. It was annexed to the Angle kingdom of Mercia by King Offa in the 8th century, in subsequent centuries, the area suffered repeated Danish invasion, and fortresses were built at Bridgnorth and Chirbury. Many defensive castles were built at this time across the county to defend against the Welsh and enable effective control of the region, including Ludlow Castle, the western frontier with Wales was not finally determined until the 14th century. Also in this period, a number of foundations were formed, the county largely falling at this time under the Diocese of Hereford. The county contains a number of historically significant towns, including Shrewsbury, Bridgnorth, additionally, the area around Coalbrookdale in the county is seen as highly significant, as it is regarded as one of the birthplaces of the Industrial Revolution. The village of Edgmond, near Newport, is the location of the lowest recorded temperature in England, the origin of the name Shropshire is the Old English Scrobbesbyrigscīr, which means Shrewsburyshire. The name may, therefore, be derived indirectly from a name such as Scrope. Salop is an old name for Shropshire, historically used as a form for post or telegrams

Shropshire, England
–
Section of Offa's Dyke near the Shropshire town of Clun, constructed after the Saxon annexation of the area in the 8th century AD.
Shropshire, England
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Flag
Shropshire, England
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The Iron Bridge at Ironbridge.
Shropshire, England
–
The River Severn, seen here in Shrewsbury, is the primary watercourse in the county.

40.
Tracheophyte
–
They also have a specialized non-lignified tissue to conduct products of photosynthesis. Vascular plants include the clubmosses, horsetails, ferns, gymnosperms and angiosperms, scientific names for the group include Tracheophyta and Tracheobionta. Vascular plants are distinguished by two characteristics, Vascular plants have vascular tissues which distribute resources through the plant. This feature allows vascular plants to evolve to a larger size than non-vascular plants, in vascular plants, the principal generation phase is the sporophyte, which is usually diploid with two sets of chromosomes per cell. Only the germ cells and gametophytes are haploid, by contrast, the principal generation phase in non-vascular plants is the gametophyte, which is haploid with one set of chromosomes per cell. In these plants, only the spore stalk and capsule are diploid, in other words, elaboration of the spore stalk enabled the production of more spores, and enabled the development of the ability to release them higher and to broadcast them farther. Such developments may include more photosynthetic area for the structure, the ability to grow independent roots, woody structure for support. A proposed phylogeny of the plants after Kenrick and Crane is as follows. Pteridophyta from Smith et al. and lycophytes and ferns by Christenhusz et al and this phylogeny is supported by several molecular studies. Other researchers state that taking fossils into account leads to different conclusions, water and nutrients in the form of inorganic solutes are drawn up from the soil by the roots and transported throughout the plant by the xylem. Organic compounds such as produced by photosynthesis in leaves are distributed by the phloem sieve tube elements. The xylem consists of vessels in flowering plants and tracheids in other vascular plants, a tracheid cell wall usually contains the polymer lignin. The phloem however consists of living cells called sieve-tube members, between the sieve-tube members are sieve plates, which have pores to allow molecules to pass through. Sieve-tube members lack such organs as nuclei or ribosomes, but cells next to them, the most abundant compound in all plants, as in all cellular organisms, is water which serves an important structural role and a vital role in plant metabolism. Transpiration is the process of water movement within plant tissues. Water is constantly transpired from the plant through its stomata to the atmosphere, the movement of water out of the leaf stomata creates a transpiration pull or tension in the water column in the xylem vessels or tracheids. The pull is the result of surface tension within the cell walls of the mesophyll cells. The draw of water upwards may be passive and can be assisted by the movement of water into the roots via osmosis

41.
Gondwana
–
In paleogeography, Gondwana, also Gondwanaland, is the name given to an ancient supercontinent. It is believed to have sutured about 600 to 530 million years ago, Gondwana formed prior to Pangaea, and later became part of it. Around 335 to 250 million years ago Gondwana and Laurasia joined together to form the supercontinent Pangaea, Gondwana then separated from Laurasia in the breakup of Pangaea, drifting farther south after the split. Gondwana itself then also broke apart, the continent of Gondwana was named by Austrian scientist Eduard Suess, after the Gondwana region of central northern India which is derived from Sanskrit for forest of the Gonds. The name had previously used in a geological context, first by H. B. From which the Gondwana sedimentary sequences are also described, for example, the plant family Proteaceae, known only from southern South America, South Africa, Australia, and New Zealand, is considered to have a Gondwanan distribution. This pattern is considered to indicate an archaic, or relict. The assembly of Gondwana was a protracted process, several orogenies led to its final amalgamation 550 to 500 million years ago at the end of the Ediacaran, and into the Cambrian. These include the Brasiliano Orogeny, the East African Orogeny, the Malagasy Orogeny, the final stages of Gondwanan assembly overlapped with the opening of the Iapetus Ocean between Laurentia and western Gondwana. During this interval, the Cambrian explosion occurred and this is the Famatinian block and it formerly continued the line of the Appalachians southwards. One of the sites of Gondwanan amalgamation was the East African Orogeny. The East African Orogeny at about 650–630 Mya affected a part of Arabia, north-eastern Africa, East Africa. Collins and Windley propose that in this orogeny, Azania collided with the Congo–Tanzania–Bangweulu Block, the later Malagasy orogeny at about 550–515 Mya affected Madagascar, eastern East Africa and southern India. In it, Neoproterozoic India collided with the already combined Azania and Congo–Tanzania–Bangweulu Block, at the same time, in the Kunga Orogeny Neoproterozoic India collided with the Australia/Mawson continent. Other large continental masses, including the core cratons of North America, Europe, when Pangaea broke up, two large masses, Gondwana and Laurasia, were formed. During the late Paleozoic, Gondwana extended from a point at or near the South Pole to near the Equator, across much of Gondwana, the climate was mild. During the Mesozoic, the world was on average warmer than it is today. Gondwana was then host to a variety of flora and fauna for many millions of years

Gondwana
–
Reconstruction showing final stages of assembly of Gondwana, 550 Mya
Gondwana
–
Map of Pangaea with Laurasia and Gondwana. 200 mya
Gondwana
–
The Nothofagus plant genus illustrates Gondwanan distribution, having descended from the supercontinent and existing in present-day Australia, New Zealand, New Caledonia, and the Southern Cone. Fossils have also recently been found in Antarctica.

42.
Millipedes
–
Each double-legged segment is a result of two single segments fused together. Most millipedes have very elongated cylindrical or flattened bodies with more than 20 segments, while pill millipedes are shorter, although the name millipede derives from the Latin for thousand feet, no known species has 1,000, the record of 750 legs belongs to Illacme plenipes. Most millipedes are slow-moving detritivores, eating decaying leaves and other plant matter. Some eat fungi or suck plant fluids, and a minority are predatory. Millipedes are generally harmless to humans, although some can become household or garden pests, most millipedes defend themselves with a variety of chemicals secreted from pores along the body, although the tiny bristle millipedes are covered with tufts of detachable bristles. Reproduction in most species is carried out by modified male legs called gonopods, first appearing in the Silurian period, millipedes are some of the oldest known land animals. Some members of prehistoric groups grew to over 2 m, the largest modern species reach lengths of 27 to 38 cm. The longest extant species is the giant African millipede, among myriapods, millipedes have traditionally been considered most closely related to the tiny pauropods, although some molecular studies challenge this relationship. Millipedes can be distinguished from the similar but only distantly related centipedes, which move rapidly, are carnivorous. The scientific study of millipedes is known as diplopodology, and a scientist who studies them is called a diplopodologist. The scientific name Diplopoda comes from the Ancient Greek words διπλοῦς, double and ποδός, foot, the common name millipede is a compound word formed from the Latin roots mille and ped. The term millipede is widespread in popular and scientific literature, but among North American scientists, other vernacular names include thousand-legger or simply diplopod. The science of biology and taxonomy is called diplopodology, the study of diplopods. Approximately 12,000 millipede species have been described, estimates of the true number of species on earth range from 15,000 to as high as 80,000. Few species of millipede are at all widespread, they have very poor dispersal abilities, depending as they do on terrestrial locomotion and these factors have favoured genetic isolation and rapid speciation, producing many lineages with restricted ranges. The living members of the Diplopoda are divided into sixteen orders in two subclasses, the basal subclass Penicillata contains a single order, Polyxenida. The higher-level classification of millipedes is presented below, based on Shear,2011, the placement and positions of extinct groups known only from fossils is tentative and not fully resolved. After each name is listed the author citation, the name of the person who coined the name or defined the group, early forms probably ate mosses and primitive vascular plants

43.
Ludlow
–
Ludlow is a market town in Shropshire, England,28 miles south of Shrewsbury and 23 miles north of Hereford via the main A49 road, which bypasses the town. With a population of approximately 11,000, Ludlow is the largest town in south Shropshire, the town is significant in the history of the Welsh Marches and neighbouring Wales. The town is near the confluence of the rivers Corve and Teme, the oldest part is the medieval walled town, founded in the late 11th century after the Norman conquest of England. It is centred on a hill which lies on the eastern bank of a bend of the River Teme. Atop this hill is Ludlow Castle and the church, St Laurences. From there the streets slope downward to the River Teme, the town is in a sheltered spot beneath Mortimer Forest and the Clee Hills, which are clearly visible from the town. Ludlow has nearly 500 listed buildings, including examples of medieval, the town was described by Sir John Betjeman as probably the loveliest town in England. The placename Lodelowe was in use for this site before 1138, at the time this section of the River Teme contained rapids, and so the hlud of Ludlow came from the loud waters, while hlaw meant hill or tumulus. Thus the name Ludlow describes a place on a hill by the loud waters, some time around the 12th century weirs were added along the river, taming these rapid flows. The hill is that which the stands on, and a pre-historic burial mound which existed at the summit of the hill could explain the tumulus variation of the hlaw element. Ludford, a neighbouring and older settlement, situated on the bank of the Teme. Ludlow has a name in the Welsh language, Llwydlo, though the town became known as Ludlow, Fouke le Fitz Waryn states that it was called Dinham for a very long time. The castle was originally called Dinham Castle, before it took on the name of Ludlow, the town is situated close to Wales, and lies near the midpoint of the 257 km long England-Wales border, it is also very close to the county border between Shropshire and Herefordshire. This strategic location invested it with national importance in times, and thereafter with the town being the seat of the Council of Wales. At the time of the Domesday Book survey, the area was part of the large Stanton parish and manor, neither Ludlow nor Dinham are mentioned in the Book, compiled in 1086, although the Book recorded manors and not settlements per se. The Book does record a number of households and taxable value for Stanton. Neighbouring places Ludford, the Sheet and Steventon do feature in the Book, as they were manors, the manor of Stanton came within the hundred of Culvestan, but during the reign of Henry I this Saxon hundred was merged into the new Munslow hundred. Walters son Roger de Lacy began the construction of Ludlow Castle on the crest of the hill about 1075, between about 1090 and 1120, the Chapel of St. Mary Magdalene was built inside the walls, and by 1130 the Great Tower was added to form the gatehouse

Ludlow
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Wintertime Ludlow as seen from Whitcliffe
Ludlow
–
Ludlow Castle built in the late 11th century.
Ludlow
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The town's outdoor market, in Castle Square, photographed from St Laurence's Church.
Ludlow
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The Feathers Hotel, one of Ludlow's more famous timber-framed buildings.

44.
Ludford, Shropshire
–
Ludford is a small village and civil parish in south Shropshire, England. The parish is situated adjacent to the town of Ludlow and was, until 1895. The village is situated on the bank of the River Teme, with Ludlow on the north bank. The village is notable with its Ludford Corner. The place name means the ford at the waters, Ludlows name means the hill by the loud waters. The loud waters are those of the River Teme, which flow rapidly through the area, Ludford, Steventon, and the Sheet are all mentioned in the Domesday Book of 1086 as manors. They existed prior to the town of Ludlow, which grew up during or after the construction of the Norman castle there, historically the parish was divided between Shropshire and Herefordshire and the village itself, despite its proximity to the Salopian town of Ludlow, fell within Herefordshire. Steventon and the Sheet on the hand were in Shropshire. Also as a result of the same 1894 Act of Parliament, Steventon, the Sheet and Holdgate Fee became part of Munslow hundred after Culvestans dissolution, as did Ludlow. The Herefordshire element of the parish remained as part of Wolphy hundred throughout until its transfer to Shropshire in 1895, during the Wars of the Roses, a minor battle was fought at Ludford in 1459, which became known as the Battle of Ludford Bridge. The village contains a country house – Ludford House –. It originated as the manor house and was acquired in 1607 by the Charlton family. Sir Job Charlton, speaker of the House of Commons, was created a baronet in 1686, the Charlton baronetcy however has since become extinct. By the 1840s the parkland had become enclosed and used as farmland, the turnpike road to Hereford, now the B4361, was built through the parkland of Ludford House in the 1820s and passes right by the back of the House. Ludford House is no longer one residence and has divided into separate dwellings. Park Road, no longer a through-road, was once the main thoroughfare leading southwards from the ford, and later the bridge, Whitcliffe Road begins at the B4361 in the centre of Ludford, heads across Whitcliffe Common towards Mortimer Forest, and runs eventually to Wigmore. National Cycle Network route 44 runs through the area, avoiding the main roads, the civil parish of Ludford runs along the south and east boundaries of Ludlow and includes the settlements of Ludford, the Sheet, Foldgate, Rocks Green and Steventon. It is effectively divided by the River Teme into two-halves, the parish council meets outwith the parish, in Ludlow

Ludford, Shropshire
–
The view from St Giles churchyard, showing St Giles Hospital and The Old Bell
Ludford, Shropshire
–
The view north across the Teme from the eastern part of Ludford village, with the skyline of Ludlow dominated by St Laurence's Church.
Ludford, Shropshire
–
Looking downstream from Ludford Bridge at the Horseshoe Weir. The former ford was just below where the weir now is, roughly where the river turns slightly to the left. The part of Ludlow on the north bank just beyond the ford remained part of the parish of Ludford until 1901.
Ludford, Shropshire
–
Viewed from downstream and the Ludlow side, Ludford Bridge, which now takes the B4361 road across the River Teme. The large public house, the Charlton Arms, is just behind.

45.
Czech Republic
–
The Czech Republic, also known as Czechia, is a nation state in Central Europe bordered by Germany to the west, Austria to the south, Slovakia to the east and Poland to the northeast. The Czech Republic covers an area of 78,866 square kilometres with mostly temperate continental climate and it is a unitary parliamentary republic, has 10.5 million inhabitants and the capital and largest city is Prague, with over 1.2 million residents. The Czech Republic includes the territories of Bohemia, Moravia. The Czech state was formed in the late 9th century as the Duchy of Bohemia under the Great Moravian Empire, after the fall of the Empire in 907, the centre of power transferred from Moravia to Bohemia under the Přemyslid dynasty. In 1002, the duchy was formally recognized as part of the Holy Roman Empire, becoming the Kingdom of Bohemia in 1198 and reaching its greatest territorial extent in the 14th century. Following the Battle of Mohács in 1526, the whole Crown of Bohemia was gradually integrated into the Habsburg Monarchy alongside the Archduchy of Austria, the Protestant Bohemian Revolt against the Catholic Habsburgs led to the Thirty Years War. After the Battle of the White Mountain, the Habsburgs consolidated their rule, reimposed Roman Catholicism, the Czech part of Czechoslovakia was occupied by Germany in World War II, and was liberated in 1945 by the armies of the Soviet Union and the United States. The Czech country lost the majority of its German-speaking inhabitants after they were expelled following the war, the Communist Party of Czechoslovakia won the 1946 elections. Following the 1948 coup détat, Czechoslovakia became a one-party communist state under Soviet influence, in 1968, increasing dissatisfaction with the regime culminated in a reform movement known as the Prague Spring, which ended in a Soviet-led invasion. Czechoslovakia remained occupied until the 1989 Velvet Revolution, when the communist regime collapsed, on 6 March 1990, the Czech Socialistic Republic was renamed to the Czech Republic. On 1 January 1993, Czechoslovakia peacefully dissolved, with its constituent states becoming the independent states of the Czech Republic and the Slovak Republic. The Czech Republic joined NATO in 1999 and the European Union in 2004, it is a member of the United Nations, the OECD, the OSCE, and it is a developed country with an advanced, high income economy and high living standards. The UNDP ranks the country 14th in inequality-adjusted human development, the Czech Republic also ranks as the 6th most peaceful country, while achieving strong performance in democratic governance. It has the lowest unemployment rate in the European Union, the traditional English name Bohemia derives from Latin Boiohaemum, which means home of the Boii. The current name comes from the endonym Čech, spelled Cžech until the reform in 1842. The name comes from the Slavic tribe and, according to legend, their leader Čech, the etymology of the word Čech can be traced back to the Proto-Slavic root *čel-, meaning member of the people, kinsman, thus making it cognate to the Czech word člověk. The country has traditionally divided into three lands, namely Bohemia in the west, Moravia in the southeast, and Czech Silesia in the northeast. Following the dissolution of Czechoslovakia at the end of 1992, the Czech part of the former nation found itself without a common single-word geographical name in English, the name Czechia /ˈtʃɛkiə/ was recommended by the Czech Ministry of Foreign Affairs

46.
Cadastre
–
A cadastre, using a cadastral survey or cadastral map, is a comprehensive register of the real estate or real propertys metes-and-bounds of a country. In most countries, legal systems have developed around the administrative systems and use the cadastre to define the dimensions. The cadastre is a source of data in disputes and lawsuits between landowners. In the United States, Cadastral Survey within the Bureau of Land Management maintains records of all public lands, such surveys often require detailed investigation of the history of land use, legal accounts, and other documents. A cadastre commonly includes details of the ownership, the tenure, the location, the dimensions, the cultivations if rural. Cadastres are used by nations around the world, some in conjunction with other records. The International Federation of Surveyors defines cadastre as follows, A Cadastre is normally a parcel based, the word forms the adjective cadastral, used in public administration, primarily for ownership and taxation purposes. The terminology for cadastral divisions may include counties, parishes, ridings, hundreds, sections, lots, blocks, other languages have kept the original t sound in the second syllable. In modern Greek, though, it has replaced by κτηματολόγιο /ktimatologio/. Some of the earliest cadasters were ordered by Roman Emperors to recover state owned lands that had appropriated by private individuals. In this way Vespasian was able to reimpose taxation formerly uncollected on these lands, with the fall of Rome the use of cadastral maps effectively discontinued. Medieval practice used written descriptions of the extent of land rather than using more precise surveys, only in the sixteenth and early seventeenth centuries did the use of cadastral maps resume, beginning in the Netherlands. With the emergence of capitalism in Renaissance Europe the need for cadastral maps reemerged as a tool to determine and this took place first privately in land disputes and later spread to governmental practice as a means of more precise tax assessment. Cadastral surveys document the boundaries of land ownership, by the production of documents, diagrams, sketches, plans, charts and they were originally used to ensure reliable facts for land valuation and taxation. An example from early England is the Domesday Book in 1086, napoleon established a comprehensive cadastral system for France that is regarded as the forerunner of most modern versions. The Public Lands Survey System is a survey of the United States originating in legislation from 1785. The Dominion Land Survey is a cadastral survey conducted in Western Canada begun in 1871 after the creation of the Dominion of Canada in 1867. Both cadastral surveys are made relative to principal meridian and baselines and these cadastral surveys divided the surveyed areas into townships, square land areas of approximately 36 square miles

47.
Estonia
–
Estonia, officially the Republic of Estonia, is a country in the Baltic region of Northern Europe. It is bordered to the north by the Gulf of Finland, to the west by the Baltic Sea, to the south by Latvia, across the Baltic Sea lies Sweden in the west and Finland in the north. The territory of Estonia consists of a mainland and 2,222 islands and islets in the Baltic Sea, covering 45,339 km2 of land and water, and is influenced by a humid continental climate. The territory of Estonia has been inhabited since at least 6500 BC, in 1988, during the Singing Revolution, the Estonian Supreme Soviet issued the Estonian Sovereignty Declaration in defiance of Soviet rule, and independence was restored on 20 August 1991. Estonia is a parliamentary republic divided into fifteen counties. Its capital and largest city is Tallinn, with a population of 1.3 million, it is one of the least-populous member states of the European Union, Eurozone, North Atlantic Treaty Organization, OECD and Schengen Area. Estonia is a country with an advanced, high-income economy that is among the fastest growing in the EU. Its Human Development Index ranks very highly, and it performs favourably in measurements of economic freedom, civil liberties, the 2015 PISA test places Estonian high school students 3rd in the world, behind Singapore and Japan. Citizens of Estonia are provided with health care, free education. Since independence the country has developed its IT sector, becoming one of the worlds most digitally advanced societies. In 2005 Estonia became the first nation to hold elections over the Internet, in the Estonian language, the oldest known endonym of the Estonians was maarahvas, meaning country people or people of the land. The land inhabited by Estonians was called Maavald meaning Country Parish or Land Parish, one hypothesis regarding the modern name of Estonia is that it originated from the Aesti, a people described by the Roman historian Tacitus in his Germania. The historic Aesti were allegedly Baltic people, whereas the modern Estonians are Finno-Ugric, the geographical areas between Aesti and Estonia do not match, with Aesti being further down south. Ancient Scandinavian sagas refer to a land called Eistland, as the country is called in Icelandic. Early Latin and other ancient versions of the name are Estia and Hestia, esthonia was a common alternative English spelling prior to 1921. Human settlement in Estonia became possible 13,000 to 11,000 years ago, the oldest known settlement in Estonia is the Pulli settlement, which was on the banks of the river Pärnu, near the town of Sindi, in south-western Estonia. According to radiocarbon dating it was settled around 11,000 years ago, the earliest human inhabitation during the Mesolithic period is connected to Kunda culture, which is named after the town of Kunda in northern Estonia. At that time the country was covered with forests, and people lived in communities near bodies of water

48.
Sandstone
–
Sandstone is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz or feldspar because these are the most common minerals in the Earths crust, like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, quartz-bearing sandstone is converted into quartzite through heating and pressure, usually related to tectonic compression within orogenic belts. They are formed from cemented grains that may either be fragments of a rock or be mono-minerallic crystals. The cements binding these grains together are typically calcite, clays, grain sizes in sands are defined within the range of 0.0625 mm to 2 mm. The formation of sandstone involves two principal stages, first, a layer or layers of sand accumulates as the result of sedimentation, either from water or from air. Typically, sedimentation occurs by the settling out from suspension. The most common cementing materials are silica and calcium carbonate, which are derived either from dissolution or from alteration of the sand after it was buried. Colours will usually be tan or yellow, a predominant additional colourant in the southwestern United States is iron oxide, which imparts reddish tints ranging from pink to dark red, with additional manganese imparting a purplish hue. Red sandstones are seen in the Southwest and West of Britain, as well as central Europe. The regularity of the latter favours use as a source for masonry, either as a building material or as a facing stone. These physical properties allow the grains to survive multiple recycling events. Quartz grains evolve from rock, which are felsic in origin. Feldspathic framework grains are commonly the second most abundant mineral in sandstones, Feldspar can be divided into two smaller subdivisions, alkali feldspars and plagioclase feldspars. The different types of feldspar can be distinguished under a petrographic microscope, below is a description of the different types of feldspar. Alkali feldspar is a group of minerals in which the composition of the mineral can range from KAlSi3O8 to NaAlSi3O8. Plagioclase feldspar is a group of solid solution minerals that range in composition from NaAlSi3O8 to CaAl2Si2O8. Lithic framework grains are pieces of ancient source rock that have yet to weather away to individual mineral grains, accessory minerals are all other mineral grains in a sandstone, commonly these minerals make up just a small percentage of the grains in a sandstone

49.
Mudstone
–
Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope, with increased pressure over time, the platey clay minerals may become aligned, with the appearance of fissility or parallel layering. This finely bedded material that splits readily into thin layers is called shale, the lack of fissility or layering in mudstone may be due to either original texture or the disruption of layering by burrowing organisms in the sediment prior to lithification. Mud rocks such as mudstone and shale comprise some 65% of all sedimentary rocks, mudstone looks like hardened clay and, depending upon the circumstances under which it was formed, it may show cracks or fissures, like a sun-baked clay deposit. Mudstone can be separated into categories, Siltstone – more than half of the composition is silt-sized particles. Claystone – more than half of the composition is clay-sized particles, mudstone – hardened mud, a mix of silt and clay sized particles. Mudstone can include, Shale – exhibits lamination or fissility, argillite – has undergone low-grade metamorphism. In the Dunham classification of limestones, a mudstone is a carbonate rock that contains less than 10% allochems in a carbonate mud matrix. As defined by the Dunham classification, a mudstone is more or less synonymous with calcilutite, on December 13,2016, NASA reported further evidence supporting habitability on the planet Mars as the Curiosity rover climbed higher, studying younger layers, on Mount Sharp. Also reported, the soluble element boron was detected for the first time on Mars. Since landing on Mars in August 2012, Curiosity has driven 15.0 km, mudstone on planet Mars Aeolis quadrangle Composition of Mars Timeline of Mars Science Laboratory Tonstein

50.
Caledonian orogeny
–
The Caledonian orogeny was a mountain building era recorded in the northern parts of Ireland and Britain, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occurred from the Ordovician to Early Devonian and it was caused by the closure of the Iapetus Ocean when the continents and terranes of Laurentia, Baltica and Avalonia collided. The Caledonian orogeny is named for Caledonia, the Latin name for Scotland, the name was first used in 1885 by Austrian geologist Eduard Suess for an episode of mountain building in northern Europe that predated the Devonian period. Geologists like Émile Haug and Hans Stille saw the Caledonian orogeny as one of several phases of mountain building that had occurred during Earths history. Current understanding has it that the Caledonian orogeny encompasses a number of phases that can laterally be diachronous. The name Caledonian can therefore not be used for a period of geological time. The Caledonian orogeny was one of several orogenies that would form the supercontinent Pangaea in the Late Paleozoic era. Between 650 and 550 million years ago the smaller continents of Laurentia, Baltica, in the process, the Iapetus Ocean between Gondwana, Baltica and Laurentia closed. In the Early Ordovician period the microcontinent Avalonia began to separate from the margin of Gondwana. Some early phases of deformation and/or metamorphism are recognized in the Scandinavian Caledonides, the first phase that is often included in the Caledonian orogeny is the Finnmarkian phase at 505 million years ago. Another phase was the Jämtlandian phase at 455 million years ago and these phases are explained by the assumption that the western edge of Baltica collided with an island arc or microcontinent. In a similar way, the edge of Laurentia collided with an island arc during the Taconic orogeny. During the Ordovician, the continent of Avalonia moved independently in a northeastern direction towards Baltica. This motion was accommodated by the subduction of the southeastern Iapetus Ocean beneath eastern Avalonia, in the Late Ordovician continental collision started between Avalonia and Baltica. The Tornquist Sea disappeared in the process, the suture is the Tornquist line. The main phase of the Caledonian orogeny is called the Scandian phase in Scandinavia and it was caused by the collision between Laurentia and Baltica. The Iapetus Ocean first closed in the north, then in the south, therefore, the collision between Baltica and Laurentia took place a little earlier than that between Avalonia and Laurentia. Continental collision started in the Mid Silurian and mountain building took place in the Early Devonian, in North America, the collision between Avalonia and Laurentia is called the Acadian orogeny

Caledonian orogeny
–
Location of the different branches of the Caledonian/ Acadian belts at the end of the Caledonian orogeny (Early Devonian). Present day coastlines are indicated in gray for reference. Later in geological history, the Atlantic Ocean opened and the different parts of the orogenic belt moved apart.

51.
Unconformity
–
An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the layer was exposed to erosion for an interval of time before deposition of the younger. The significance of angular unconformity was shown by James Hutton, who found examples of Huttons Unconformity at Jedburgh in 1787, the rocks above an unconformity are younger than the rocks beneath. An unconformity represents time during which no sediments were preserved in a region, the local record for that time interval is missing and geologists must use other clues to discover that part of the geologic history of that area. The interval of time not represented is called a hiatus. A disconformity is an unconformity between parallel layers of rocks which represents a period of erosion or non-deposition. Disconformities are marked by features of subaerial erosion and this type of erosion can leave channels and paleosols in the rock record. A paraconformity is a type of disconformity in which the separation is a simple bedding plane with no obvious buried erosional surface. A nonconformity exists between sedimentary rocks and metamorphic or igneous rocks when the rock lies above and was deposited on the pre-existing. Namely, if the rock below the break is igneous or has lost its bedding due to metamorphism, the whole sequence may later be deformed and tilted by further orogenic activity. A typical case history is presented by the evolution of the Briançonnais realm during the Jurassic. A paraconformity is a type of unconformity in which strata are parallel, there is no apparent erosion and it is also called nondepositional unconformity or pseudoconformity. A buttress unconformity occurs when younger bedding is deposited against older strata thus influencing its bedding structure. S, bureau of Mines Dictionary of Mining, Mineral, and Related Terms published on CD-ROM in 1996

52.
Continental Drift
–
Continental drift is the movement of the Earths continents relative to each other, thus appearing to drift across the ocean bed. The speculation that continents might have drifted was first put forward by Abraham Ortelius in 1596, the concept was independently and more fully developed by Alfred Wegener in 1912, but his theory was rejected by some for lack of a mechanism and others because of prior theoretical commitments. The idea of continental drift has been subsumed by the theory of plate tectonics, W. J. Kious described Ortelius thoughts in this way, Abraham Ortelius in his work Thesaurus Geographicus. Suggested that the Americas were torn away from Europe and Africa, by earthquakes and floods and went on to say, The vestiges of the rupture reveal themselves, if someone brings forward a map of the world and considers carefully the coasts of the three. In his Manual of Geology,1863, Dana says The continents, Dana was enormously influential in America – his Manual of Mineralogy is still in print in revised form – and the theory became known as Permanence theory. This suggested that the oceans were a permanent feature of the earths surface and this led Mantovani to propose an Expanding Earth theory which has since been shown to be incorrect. Continental drift without expansion was proposed by Frank Bursley Taylor, who suggested in 1908 that the continents were moved into their present positions by a process of continental creep. Wegener said that of all theories, Taylors, although not fully developed, had the most similarities to his own. In the mid-20th century, the theory of drift was referred to as the Taylor-Wegener hypothesis. Alfred Wegener first presented his hypothesis to the German Geological Society on January 6,1912 and his hypothesis was that the continents had once formed a single landmass, called Pangea, before breaking apart and drifting to their present locations. Wegener was the first to use the continental drift and formally publish the hypothesis that the continents had somehow drifted apart. Although he presented evidence for continental drift, he was unable to provide a convincing explanation for the physical processes which might have caused this drift. The Polflucht hypothesis was studied by Paul Sophus Epstein in 1920. The theory of drift was not accepted for many years. One problem was that a driving force was missing. A second problem was that Wegeners estimate of the velocity of continental motion,250 cm/year, was implausibly high, and it did not help that Wegener was not a geologist. Other geologists also believed that the evidence that Wegener had provided was not sufficient, the British geologist Arthur Holmes championed the theory of continental drift at a time when it was deeply unfashionable. He proposed in 1931 that the Earths mantle contained convection cells that dissipated radioactive heat and his Principles of Physical Geology, ending with a chapter on continental drift, was published in 1944

53.
Euramerica
–
Euramerica was a minor supercontinent created in the Devonian as the result of a collision between the Laurentian, Baltica, and Avalonia cratons,433 million years ago. In the Late Carboniferous, tropical rainforests lay over the equator of Euramerica, a major, abrupt change in vegetation occurred when the climate aridified. The forest fragmented and the lycopsids which dominated these wetlands thinned out, there was also a great loss of amphibian diversity and simultaneously the drier climate spurred the diversification of reptiles. Euramerica became a part of the major supercontinent Pangaea in the Permian, in the Jurassic, when Pangaea rifted into two continents, Gondwana and Laurasia, Euramerica was a part of Laurasia. In the Cretaceous, Laurasia split into the continents of North America, the Laurentian craton became a part of North America while Baltica became a part of Eurasia, and Avalonia was split between the two. Permian, Euramerica became a part of the supercontinent Pangaea, Jurassic, Pangaea rifted into Gondwana and Laurasia. Cretaceous, Laurasia split into the continents of North America and Eurasia, continental drift Eurasia Main Uralian Fault Palaeos Earth, Geography, Euramerica Paleogeographic globe of the Devonian Earth

Euramerica
–
Euramerica in the Devonian

54.
Panthalassa
–
Panthalassa, also known as the Panthalassic or Panthalassan Ocean, was the superocean that surrounded the supercontinent Pangaea. During the Paleozoic—Mesozoic transition c.250 Ma it occupied almost 70% of Earths surface and its ocean-floor has completely disappeared because of the continuous subduction along the continental margins on its circumference. Panthalassa is also referred to as the Paleo-Pacific or Proto-Pacific because the Pacific Ocean developed from its centre in the Mesozoic to the present, the supercontinent Rodinia began to break-up 870–845 Ma probably as a consequence of a superplume caused by mantle slab avalanches along the margins of the supercontinent. In the Late Jurassic the Pacific Plate opened originating from a junction between the Panthalassic Farallon, Phoenix, and Izanagi plates. Panthalassa can be reconstructed based on magnetic lineations and fracture zones preserved in the western Pacific, in western Laurentia, a tectonic episode that preceded this rifting produced failed rifts that harboured large depositional basins in Western Laurentia. The global ocean of Mirovia, an ocean that surrounded Rodinia, started to shrink as the Pan-African ocean, between 650 million and 550 million years ago, another supercontinent started to form, Pannotia, which was shaped like a V. Inside the V was Panthalassa, outside of the V were the Pan-African Ocean, furthermore, seismic tomography is being used to identify subducted slabs in the mantle, from which the location of former Panthalassic subduction zones can be derived. A series of such zones, called Telkhinia, defines two separate oceans or systems of oceanic plates — the Pontus and Thalassa oceans. Named marginal oceans or oceanic plates include Mongol-Okhotsk, Oimyakon, Slide Mountain Ocean, the western margin of Laurentia originated during the Neoproterozoic break-up of Rodinia. The North American Cordillera is an accretionary orogen which grew by the addition of allochthonous terranes along this margin from the Late Palaeozoic. Devonian back-arc volcanism reveals how this eastern Panthalassic margin developed into the margin it still is in the mid-Palaeozoic. Most of the fragments, volcanic arcs, and ocean basins added to Laurentia this way contained faunas of Tethyan or Asian affinity. Similar terranes added to the northern Laurentia, in contrast, have affinities with Baltica, Siberia, and these latter terranes were probably accreted along the eastern Panthalassa margin by a Caribbean–Scotia-style subduction system. Today the region is dominated by the collision of the Australian Plate with a network of plate boundaries in south-east Asia. Spreading along the Pacific-Phoenix ridge ended 83 Ma at the Osbourn Trough at the Tonga-Kermadec Trench, during the Permian atolls developed near the Equator on the mid-Panthalassic seamounts. One such migrating atoll complex now form a 2-kilometre-long and 100-to-150-metre-wide body of limestone in central Kyushu, south-west Japan. The Permian–Triassic extinction event c.260 Ma, however, put an end to development with only dwarf taxa persisting throughout the Permian until the final fusuline extinction c.252 Ma. Permian fusulines also developed a remarkable provincialism by which fusulines can be grouped into six domains, because of the large size of Panthalassa a hundred million years could separate the accretion of different groups of fusulines

55.
Paleo-Tethys
–
Paleo-Tethys was a precursor to the Tethys Ocean which was located between Gondwana and the Hunic terranes. It opened as the Proto-Tethys Ocean subducted under these terranes and closed as the Cimmerian terranes gave way to the Tethys Ocean. e, the so-called Hunic terranes are divided into the European Hunic and Asiatic Hunic. A large transform fault separated the two terranes, the role the Paleo-Tethys played in the supercontinent cycle, and especially the break-up of Pangaea, is unresolved. The Paleo-Tethys Ocean began to form when back-arc spreading separated the European Hunic terranes from Gondwana in the late Ordovician, in the Early Devonian, the eastern part of Paleo-Tethys opened up, when the Asiatic Hunic terranes, including the North and South China microcontinents, moved northward. These events caused Proto-Tethys Ocean, a precursor of Paleo-Tethys, to shrink, until the Late Carboniferous, in the Early Carboniferous however, a subduction zone developed south of the European Hunic terranes consuming Paleo-Tethys oceanic crust. Gondwana started moving north, in the process the part of the Paleo-Tethys would close. The Rheic Ocean had completely disappeared, and the western Paleo-Tethys was closing, by the Late Permian, the small elongated Cimmerian plate broke away from Gondwana. South of the Cimmerian continent a new ocean, the Tethys Ocean, was created, by the Late Triassic, all that was left of the Paleo-Tethys Ocean was a narrow seaway. In the Early Jurassic epoch, as part of the Alpine Orogeny, a last remnant of Paleo-Tethys Ocean might be an oceanic crust under the Black Sea. The Paleo-Tethys Ocean sat where the Indian Ocean and Southern Asia are now located, the Equator ran the length of the sea, giving it a tropical climate. The shores and islands probably supported dense coal forests, Late Carboniferous Map - at PaleoMap Project, a good picture of Paleo-Tethys Ocean before the Cimmerian Plate moves northward. Paleo-Tethys and Proto-Tethys - at global history

Paleo-Tethys
–
Paleo-Tethys Ocean 280 million years ago

56.
Earth
–
Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun

Earth
–
" The Blue Marble " photograph of Earth, taken during the Apollo 17 lunar mission in 1972
Earth
–
Artist's impression of the early Solar System's planetary disk
Earth
–
World map color-coded by relative height
Earth
–
The summit of Chimborazo, in Ecuador, is the point on Earth's surface farthest from its center.

57.
Greenhouse
–
A greenhouse is a structure with walls and roof made chiefly of transparent material, such as glass, in which plants requiring regulated climatic conditions are grown. These structures range in size from small sheds to industrial-sized buildings, a miniature greenhouse is known as a cold frame. The interior of a greenhouse exposed to sunlight becomes significantly warmer than the ambient temperature. Many commercial glass greenhouses or hothouses are high tech production facilities for vegetables or flowers, the glass greenhouses are filled with equipment including screening installations, heating, cooling, lighting, and may be controlled by a computer to optimize conditions for plant growth. Different techniques are used to evaluate optimality-degrees and comfort ratio of greenhouse micro-climate in order to reduce production risk prior to cultivation of a specific crop. The idea of growing plants in environmentally controlled areas has existed since Roman times, the Roman emperor Tiberius ate a cucumber-like vegetable daily. The Roman gardeners used artificial methods of growing to have it available for his every day of the year. Cucumbers were planted in wheeled carts which were put in the sun daily, the cucumbers were stored under frames or in cucumber houses glazed with either oiled cloth known as specularia or with sheets of selenite, according to the description by Pliny the Elder. In the 13th century, greenhouses were built in Italy to house the plants that explorers brought back from the tropics. They were originally called giardini botanici, Greenhouses in which the temperature could be manually manipulated first appeared in 15th century Korea. The 15th century treatise, the Sanga Yorok, contains descriptions of greenhouses designed to regulate the temperature and humidity requirements of plants, the concept of greenhouses also appeared in the Netherlands and then England in the 17th century, along with the plants. Some of these early attempts required enormous amounts of work to close up at night or to winterize, there were serious problems with providing adequate and balanced heat in these early greenhouses. Today, the Netherlands has many of the largest greenhouses in the world, the French botanist Charles Lucien Bonaparte is often credited with building the first practical modern greenhouse in Leiden, Holland, during the 1800s to grow medicinal tropical plants. Originally only on the estates of the rich, the growth of the science of botany caused greenhouses to spread to the universities, the French called their first greenhouses orangeries, since they were used to protect orange trees from freezing. As pineapples became popular, pineries, or pineapple pits, were built, experimentation with the design of greenhouses continued during the 17th century in Europe, as technology produced better glass and construction techniques improved. The greenhouse at the Palace of Versailles was an example of their size and elaborateness, it was more than 150 metres long,13 metres wide, a good example of this trend is the pioneering Kew Gardens. Other large greenhouses built in the 19th century included the New York Crystal Palace, Munich’s Glaspalast, in Japan, the first greenhouse was built in 1880 by Samuel Cocking, a British merchant who exported herbs. In the 20th century, the dome was added to the many types of greenhouses

58.
Brachiopods
–
Brachiopods, phylum Brachiopoda, are a group of lophotrochozoan animals that have hard valves on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the end, while the front can be opened for feeding or closed for protection. Two major groups are recognized, articulate and inarticulate, the word brachiopod is formed from the Ancient Greek words βραχίων and πούς. They are often known as shells, since the curved shells of the class Terebratulida look rather like pottery oil-lamps. Lifespans range from three to thirty years. Ripe gametes float from the gonads into the coelom and then exit into the mantle cavity. The larvae of inarticulate brachiopods are miniature adults, with lophophores that enable the larvae to feed, traditionally, brachiopods have been regarded as members of, or as a sister group to, the deuterostomes, a superphylum that includes chordates and echinoderms. Lineages of brachiopods that have both fossil and extant taxa appeared in the early Cambrian, Ordovician, and Carboniferous periods, other lineages have arisen and then become extinct, sometimes during severe mass extinctions. Brachiopod fossils have been useful indicators of climate changes during the Paleozoic, however, after the Permian–Triassic extinction event, brachiopods recovered only a third of their former diversity. A study in 2007 concluded the brachiopods were especially vulnerable to the Permian–Triassic extinction, as they built calcareous hard parts and had low metabolic rates, Brachiopods live only in the sea, and most species avoid locations with strong currents or waves. The larvae of articulate species settle in quickly and form dense populations in well-defined areas while the larvae of inarticulate species swim for up to a month and have wide ranges, Brachiopods now live mainly in cold water and low light. Fish and crustaceans seem to find brachiopod flesh distasteful and seldom attack them, among brachiopods, only the lingulids have been fished commercially, on a very small scale. One brachiopod species may be a measure of environmental conditions around an oil terminal being built in Russia on the shore of the Sea of Japan, modern brachiopods range from 1 to 100 millimetres long, and most species are about 10 to 30 millimetres. The largest brachiopods known – Gigantoproductus and Titanaria, reaching 30 to 38 centimetres in width – occurred in the part of the Lower Carboniferous. Each has two valves which cover the dorsal and ventral surface of the animal, unlike bivalve molluscs whose shells cover the lateral surfaces, the valves are termed brachial and pedicle. The brachial valve bears on its inner surface the brachia from which the phylum gets its name, the pedicle valve has on its inner surface the attachment to the stalk-like pedicle by which most brachiopods attach themselves to the substrate. The pedicle valve is larger than the brachial. In most articulate brachiopod species, both valves are convex, the surfaces often bearing growth lines and/or other ornamentation, however, inarticulate lingulids, which burrow into the seabed, have valves that are smoother, flatter and of similar size and shape

59.
Osteichthyes
–
Osteichthyes /ˌɒstiːˈɪkθi. iːz/, popularly referred to as the bony fish, is a diverse taxonomic group of fish that have skeletons primarily composed of bone tissue, as opposed to cartilage. The vast majority of fish are members of Osteichthyes, which is a diverse and abundant group consisting of 45 orders. It is the largest class of vertebrates in existence today, the group Osteichthyes is divided into the ray-finned fish and lobe-finned fish. The oldest known fossils of fish are about 420 million years ago. Osteichthyes can be compared to Euteleostomi, in paleontology, the terms are synonymous. However, recently published phylogenetic trees treat the Osteichthyes as a clade, bony fish are characterized by a relatively stable pattern of cranial bones, rooted, medial insertion of mandibular muscle in the lower jaw. The head and pectoral girdles are covered with large dermal bones, the eyeball is supported by a sclerotic ring of four small bones, but this characteristic has been lost or modified in many modern species. The labyrinth in the ear contains large otoliths. The braincase, or neurocranium, is divided into anterior and posterior sections divided by a fissure. Early bony fish had simple lungs which helped them breathe in low-oxygen water, in many bony fish these have evolved into swim bladders, which help the body create a neutral balance between sinking and floating. They do not have fin spines, but instead support the fin with lepidotrichia and they also have an operculum, which helps them breathe without having to swim. Bony fish have no placoid scales, most have smooth and overlapping ganoid, cycloid or ctenoid scales. Traditionally, Osteichthyes is considered a class, recognised on having a swim bladder, under this classification systems, the Osteichthyes are paraphyletic with regard to land vertebrates as the common ancestor of all Osteichthyes includes tetrapods amongst its descendants. The largest subclass, the Actinopterygii are monophyletic, but with the inclusion of the smaller sub-class Sarcopterygii and this has led to an alternative classification, splitting the Osteichthyes into two full classes. Paradoxically, Sarcopterygii is under this scheme monophyletic, as it includes the tetrapods, most bony fish belong to the ray-finned fish. The phylogeny of living bony fishes is shown in the cladogram, for the majority this is their sole or main means of respiration. Lungfish and other species are capable of respiration through lungs or vascularized swim bladders. Other species can respire through their skin, intestines, and/or stomach, Osteichthyes are primitively ectothermic, meaning that their body temperature is dependent on that of the water

Osteichthyes
–
Blue runner
Osteichthyes
–
Guiyu oneiros, the earliest known bony fish, lived during the Late Silurian, 419 million years ago). It has the combination of both ray-finned and lobe-finned features, although analysis of the totality of its features place it closer to lobe-finned fish.
Osteichthyes
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ray-finned fish

60.
Acanthodian
–
Acanthodii or acanthodians is a paraphyletic class of extinct teleostome fish, sharing features with both bony fish and cartilaginous fish. In form they resembled sharks, but their epidermis was covered with tiny rhomboid platelets like the scales of holosteans and they represent several independent phylogenetic branch of fishes leading to the still-extant Chondrichthyes. The popular name spiny sharks is a misnomer for these early jawed fishes. Fossilized spines and scales are all that remains of these fishes in ancient sedimentary rocks. The earliest acanthodians were marine, but during the Devonian, freshwater species became predominant, there are three orders recognized, Climatiiformes, Ischnacanthiformes and Acanthodiformes. Overall, the jaws are presumed to have evolved from the first gill arch of some ancestral jawless fishes that had a gill skeleton made of pieces of jointed cartilage. The scales of Acanthodii have distinctive ornamentation peculiar to each order, because of this, the scales are often used in determining relative age of sedimentary rock. The scales are tiny, with a base, a neck. Despite being called spiny sharks, acanthodians predate sharks, the earliest unequivocal acanthodian fossils date from the beginning of the Silurian Period, some 50 million years before the first sharks appeared. Later, the acanthodians colonized fresh waters, and throve in the rivers and lakes during the Devonian and in the coal swamps of Carboniferous. By this time bony fishes were already showing their potential to dominate the waters of the world, and their competition proved too much for the spiny sharks, many palaeontologists originally considered the acanthodians close to the ancestors of the bony fishes. Although their interior skeletons were made of cartilage, a bonelike material had developed in the skins of these fishes, some scales were greatly enlarged and formed a bony covering on top of the head and over the lower shoulder girdle. Others developed a bony flap over the gill openings analogous to the operculum in later bony fishes, however, most of these characteristics are considered homologous characteristics derived from common placoderm ancestors, and present also in basal cartilaginous fish. In a study of early jawed vertebrate relationships, Davis et al. found acanthodians to be split among the two major clades Osteichthyes and Chondrichthyes, the well-known acanthodian Acanthodes was placed within Osteichthyes, despite the presence of many chondrichthyan characteristics in its braincase. Burrow et al.2016 provides vindication by finding chondrichthyans to be nested among Acanthodii, most closely related to Doliodus and Tamiobatis. A2017 study of Doliodus morphology points out that it appears to display a mosaic of shark and acanthodian features, making it a transitional fossil and further reinforcing this idea. Beneš, Josef, Prehistoric Animals and Plants, New York, Hamlyn, ISBN 978-0-600-30341-1 Janvier, Phillipe, Early vertebrates, Oxford, Clarendon Press, ISBN 978-0-19-854047-2 Long, John A. The Rise of Fishes,500 Million Years of Evolution, Baltimore, Johns Hopkins University Press, ISBN 978-0-8018-4992-3 Palmer, Douglas, the Simon & Schuster Encyclopedia of Dinosaurs & Prehistoric Creatures

61.
Gills
–
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water and excretes carbon dioxide. The gills of species, such as hermit crabs, have adapted to allow respiration on land provided they are kept moist. The microscopic structure of a gill presents a surface area to the external environment. Many microscopic aquatic animals, and some larger but inactive ones, can absorb oxygen through the entire surface of their bodies. However, more complex or more active aquatic organisms usually require a gill or gills, Gills usually consist of thin filaments of tissue, branches, or slender, tufted processes that have a highly folded surface to increase surface area. A high surface area is crucial to the gas exchange of aquatic organisms, a cubic meter of air contains about 250 grams of oxygen at STP. The concentration of oxygen in water is lower than in air, in fresh water, the dissolved oxygen content is approximately 8 cm3/L compared to that of air which is 210 cm3/L. Water is 777 times more dense than air and is 100 times more viscous, oxygen has a diffusion rate in air 10,000 times greater than in water. The use of sac-like lungs to remove oxygen from water would not be efficient enough to sustain life, rather than using lungs, aseous exchange takes place across the surface of highly vascularised gills over which a one-way current of water is kept flowing by a specialised pumping mechanism. The density of the water prevents the gills from collapsing and lying on top of each other, with the exception of some aquatic insects, the filaments and lamellae contain blood or coelomic fluid, from which gases are exchanged through the thin walls. The blood carries oxygen to other parts of the body, carbon dioxide passes from the blood through the thin gill tissue into the water. Gills or gill-like organs, located in different parts of the body, are found in groups of aquatic animals, including mollusks, crustaceans, insects, fish. The gills of vertebrates typically develop in the walls of the pharynx, most species employ a countercurrent exchange system to enhance the diffusion of substances in and out of the gill, with blood and water flowing in opposite directions to each other. The gills are composed of filaments, the gill lamellae. When a fish breathes, it draws in a mouthful of water at regular intervals, then it draws the sides of its throat together, forcing the water through the gill openings, so it passes over the gills to the outside. Fish gill slits may be the ancestors of the tonsils, thymus glands. Adjacent slits are separated by a gill arch from which projects a cartilaginous gill ray. This gill ray is the support for the sheet-like interbranchial septum, the base of the arch may also support gill rakers, projections into the pharyngeal cavity that help to prevent large pieces of debris from damaging the delicate gills

62.
Bryozoa
–
Bryozoa, are a phylum of aquatic invertebrate animals. Typically about 0.5 millimetres long, they are filter feeders that sieve food particles out of the using a retractable lophophore. Most marine species live in tropical waters, but a few occur in oceanic trenches, one class lives only in a variety of freshwater environments, and a few members of a mostly marine class prefer brackish water. Over 4,000 living species are known, one genus is solitary and the rest are colonial. The phylum was originally called Polyzoa, but this term was superseded by Bryozoa in 1831, another group of animals discovered subsequently, whose filtering mechanism looked similar, was also included in Bryozoa until 1869, when the two groups were noted to be very different internally. The more recently discovered group was given the name Entoprocta, while the original Bryozoa were called Ectoprocta, however, Bryozoa has remained the more widely used term for the latter group. Individuals in bryozoan colonies are called zooids, since they are not fully independent animals, all colonies contain autozooids, which are responsible for feeding and excretion. Colonies of some classes have various types of non-feeding specialist zooids, some of which are hatcheries for fertilized eggs, the class Cheilostomata have the largest number of species, possibly because they have the widest range of specialist zooids. A few species can creep very slowly by using spiny defensive zooids as legs, autozooids supply nutrients to non-feeding zooids by channels that vary between classes. Zooids have no special excretory organs, and the polypides of autozooids are scrapped when the polypides become overloaded by waste products, in autozooids the gut is U-shaped, with the mouth inside the crown of tentacles and the anus outside it. Colonies take a variety of forms, including fans, bushes, the Cheilostomata produce mineralized exoskeletons and form single-layered sheets which encrust over surfaces. Zooids of all the species are simultaneous hermaphrodites. Although those of marine species function first as males and then as females. All species emit sperm into the water, some also release ova into the water, while others capture sperm via their tentacles to fertilize their ova internally. In some species the larvae have large yolks, go to feed, others produce larvae that have little yolk but swim and feed for a few days before settling. After settling, all larvae undergo a metamorphosis that destroys. Freshwater species also produce statoblasts that lie dormant until conditions are favorable, predators of marine bryozoans include nudibranchs, fish, sea urchins, pycnogonids, crustaceans, mites and starfish. Freshwater bryozoans are preyed on by snails, insects, and fish, in Thailand, many populations of one freshwater species have been wiped out by an introduced species of snail

63.
Hederellid
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Hederellids are extinct colonial animals with calcitic tubular branching exoskeletons. They range from the Silurian to the Permian and were most common in the Devonian period and they are more properly known as hederelloids because they were originally defined as a suborder by Bassler, who described about 130 species. Work continues on assessing the true affinities of hederelloids, but they appear to be most closely related to phoronids, Family Hederellidae Genus Diversipora Genus Hederella Family Reptariidae Genus Cystoporella Genus Hederopsis Genus Hernodia Bassler, R. S. A suborder of Paleozoic cyclostomatous Bryozoa, Proceedings of the United States National Museum,87, 25-91. Taylor, Paul D. Olev Vinn, Mark A. Wilson, taylor, P. D. and Wilson, M. A. Morphology and affinities of hederelloid bryozoans, p. 301-309. Key, M. M. Jr. and Winston, J. E. Bryozoan Studies 2007, Proceedings of the 14th International Bryozoology Conference, Boone, North Carolina, virginia Museum of Natural History Special Publication 15. “Pseudobryozoans” and the problem of encruster diversity in the Paleozoic, predatory drillholes and partial mortality in Devonian colonial metazoans

65.
Crinoid
–
Crinoids are marine animals that make up the class Crinoidea of the echinoderms. The name comes from the Greek word krinon, a lily and they live in both shallow water and in depths as great as 9,000 meters. Those crinoids which, in their form, are attached to the sea bottom by a stalk are commonly called sea lilies. The unstalked forms are called feather stars or comatulids, crinoids are characterised by a mouth on the top surface that is surrounded by feeding arms. They have a U-shaped gut, and their anus is located next to the mouth, although the basic echinoderm pattern of fivefold symmetry can be recognised, most crinoids have many more than five arms. Crinoids usually have a used to attach themselves to a substrate. There are only about 600 extant crinoid species, but they were more abundant. Some thick limestone beds dating to the mid- to late-Paleozoic are almost entirely made up of disarticulated crinoid fragments, crinoids comprise three basic sections, the stem, the calyx, and the arms. The stem is composed of highly porous ossicles which are connected by ligamentary tissue, the calyx contains the crinoids digestive and reproductive organs, and the mouth is located at the top of the dorsal cup, while the anus is located peripheral to it. The majority of living crinoids are free-swimming and have only a vestigial stalk, in those deep-sea species that still retain a stalk, it may reach up to 1 metre in length, although it is usually much smaller. The base of the consists of a disc-like sucker, which. The stalk is lined by small cirri. Like other echinoderms, crinoids have pentaradial symmetry, the aboral surface of the body is studded with plates of calcium carbonate, forming an endoskeleton similar to that in starfish and sea urchins. These make the calyx somewhat cup-shaped, and there are few, if any, the upper surface, or tegmen, is divided into five ambulacral areas, including a deep groove from which the tube feet project, and five interambulacral areas between them. The anus, unusually for echinoderms, is found on the surface as the mouth. The ambulacral grooves extend onto the arms, which thus have tube feet along their inner surfaces, primitively, crinoids had only five arms, but in most living species these are divided into two, giving ten arms in total. In most living species, especially the free-swimming feather stars, the arms branch several times, the arms are jointed, and lined by smaller feather-like appendages, or pinnules, which also include tube feet. Crinoids feed by filtering small particles of food from the sea water with their feather like arms, the tube feet are covered with a sticky mucus that traps any food that floats past

66.
Trigonotarbida
–
The order Trigonotarbida is an extinct group of arachnids whose fossil record extends from the late Silurian to the early Permian. These animals are known from localities in Europe and North America. Trigonotarbids can be envisaged as spider-like arachnids, but without silk-producing spinnerets, probably living as predators on other arthropods, some later trigonotarbid species were quite heavily armoured and protected themselves with spines and tubercles. About seventy species are known, with most fossils originating from the Carboniferous Coal Measures. In July 2014 scientists used computer graphics to re-create a possible walking gait for the animal, the first trigonotarbid was described in 1837 from the Coal Measures of Coalbrookdale in England by the famous English geologist Dean William Buckland. He believed it to be a beetle and named it Curculoides prestvicii. A much better preserved example was discovered from Coseley near Dudley. Described in 1871 by Henry Woodward, he identified it as an arachnid and renamed it Eophrynus prestvicii – whereby the genus name comes from ἠώς, and Phrynus. This species was raised to a new, extinct, arachnid order which Karsch called Anthracomarti, the name is derived from ἄνθραξ, the Greek word for coal. A number of fossils which would eventually be placed in Trigonotarbida were discovered around this time. Hans Bruno Geinitz described Kreischeria wiedei from the Coal Measures of Zwickau in Germany, johann Kušta described Anthracomartus krejcii from Rakovník in the Czech Republic, and published further descriptions in a number of subsequent papers. In 1884, Samuel Hubbard Scudder described Anthracomartus trilobitus from Fayetteville, early studies tended to confuse trigonotarbids with other living or extinct groups of arachnids, particularly harvestmen. Petrunkevitchs division of the trigonotarbids into two, unrelated, orders was noted above, in detail, he divided the arachnids into suborders based on the width of the division between the two parts of the body. Anthracomartida and another extinct order, Haptopoda, were grouped into a subclass Stethostomata defined by a division of the body. Trigonotarbida was placed in its own subclass Soluta and defined as having a division of the body which was variable in width, petrunkevitchs scheme was largely followed in subsequent studies of fossil arachnids. In the 1980s, Bill Shear and colleagues carried out an important study on well preserved Mid Devonian trigonotarbids from Gilboa and they questioned whether it was appropriate to define a group of animals on a variable character state and carried out the first cladistic analysis of fossil and living arachnids. They showed that trigonotarbids are closely related to a group of arachnids which have gone under various names, in a 2007 study of arachnid relationships, the Shear et al. hypothesis was largely supported and a group Pantetrapulmonata was proposed which comprises Trigonotarbida + Tetrapulmonata. This has since been corroborated in more recent cladistic analyses, in 1892, Ferdinand Karsch suggested that the rare and rather bizarre looking ricinuleids were the last living descendants of the trigonotarbids

Trigonotarbida
–
Kreischeria fossil in Vienna
Trigonotarbida

67.
Invertebrate
–
Invertebrates are animals that neither possess nor develop a vertebral column, derived from the notochord. This includes all animals apart from the subphylum Vertebrata, familiar examples of invertebrates include insects, crabs, lobsters and their kin, snails, clams, octopuses and their kin, starfish, sea-urchins and their kin, jellyfish, and worms. The majority of species are invertebrates, one estimate puts the figure at 97%. Many invertebrate taxa have a number and variety of species than the entire subphylum of Vertebrata. Some of the invertebrates, such as the Tunicata and Cephalochordata are more closely related to the vertebrates than to other invertebrates. This makes the term invertebrate paraphyletic and hence almost meaningless for taxonomic purposes, the word invertebrate comes from the form of the Latin word vertebra, which means a joint in general, and sometimes specifically a joint from the spinal column of a vertebrate. In turn the jointed aspect of vertebra derived from the concept of turning, coupled with the prefix in-, meaning not or without. The term invertebrates is not always precise among non-biologists since it does not accurately describe a taxon in the way that Arthropoda. Each of these describes an valid taxon, phylum, subphylum or family. Invertebrata is a term of convenience, not a taxon, it has very little circumscriptional significance except within the Chordata, the Vertebrata as a subphylum comprises such a small proportion of the Metazoa that to speak of the kingdom Animalia in terms of Vertebrata and Invertebrata has limited practicality. That would at least circumscribe the Chordata, however, even the notochord would be a less fundamental criterion than aspects of embryological development and symmetry or perhaps bauplan. The following text reflects earlier scientific understanding of the term and of animals which have constituted it. According to this understanding, invertebrates do not possess a skeleton of bone and they include hugely varied body plans. Many have fluid-filled, hydrostatic skeletons, like jellyfish or worms, others have hard exoskeletons, outer shells like those of insects and crustaceans. The most familiar invertebrates include the Protozoa, Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Echinodermata, Mollusca, Arthropoda include insects, crustaceans and arachnids. By far the largest number of described species are insects. The following table lists the number of described extant species for major invertebrate groups as estimated in the IUCN Red List of Threatened Species,2014.3. The IUCN estimates that 66,178 extant vertebrate species have been described, the trait that is common to all invertebrates is the absence of a vertebral column, this creates a distinction between invertebrates and vertebrates

68.
Early Devonian
–
The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian,419.2 million years ago, to the beginning of the Carboniferous,358.9 Mya. It is named after Devon, England, where rocks from this period were first studied, the first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents, by the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods also became well-established, Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fish. The first ray-finned and lobe-finned bony fish appeared, while the placodermi began dominating almost every aquatic environment. The ancestors of all four-limbed vertebrates began adapting to walking on land, as their strong pectoral, in the oceans, primitive sharks became more numerous than in the Silurian and Late Ordovician. The first ammonites, species of molluscs, appeared, trilobites, the mollusk-like brachiopods and the great coral reefs, were still common. The Late Devonian extinction which started about 375 million years ago severely affected marine life, killing off all placodermi, and all trilobites, save for a few species of the order Proetida. The palaeogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, while the rock beds that define the start and end of the Devonian period are well identified, the exact dates are uncertain. According to the International Commission on Stratigraphy, the Devonian extends from the end of the Silurian 419.2 Mya, another common term is Age of the Fishes, referring to the evolution of several major groups of fish that took place during the period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian, Breconian and Farlovian stages, in the Late Devonian, by contrast, arid conditions were less prevalent across the world and temperate climates were more common. The Devonian Period is formally broken into Early, Middle and Late subdivisions, the rocks corresponding to those epochs are referred to as belonging to the Lower, Middle and Upper parts of the Devonian System. Early Devonian The Early Devonian lasted from 419.2 ±2.8 to 393.3 ±2.5 and began with the Lochkovian stage, which lasted until the Pragian. It spanned from 410.8 ±2.8 to 407.6 ±2.5, and was followed by the Emsian, which lasted until the Middle Devonian began,393. 3±2.7 million years ago. Middle Devonian The Middle Devonian comprised two subdivisions, first the Eifelian, which gave way to the Givetian 387. 7±2.7 million years ago. Late Devonian Finally, the Late Devonian started with the Frasnian,382.7 ±2.8 to 372.2 ±2.5, during which the first forests took shape on land. The first tetrapods appeared in the record in the ensuing Famennian subdivision. This lasted until the end of the Devonian,358. 9±2.5 million years ago, the Devonian was a relatively warm period, and probably lacked any glaciers

Early Devonian
–
The rocks of Lummaton Quarry in Torquay in Devon played an early role in defining the Devonian period.
Early Devonian
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Dunkleosteus, one of the largest armoured fish to ever roam the planet, lived during the late Devonian
Early Devonian
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Enrolled phacopid trilobite from the Devonian of Ohio
Early Devonian
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The common tabulate coral Aulopora from the Middle Devonian of Ohio – view of colony origin encrusting a brachiopod valve

69.
Detritivore
–
Detritivores, also known as detrivores, detritophages, detritus feeders, or detritus eaters, are heterotrophs that obtain nutrients by consuming detritus. There are many kinds of invertebrates, vertebrates and plants carry out coprophagy. By doing so, all these detritivores contribute to decomposition and the nutrient cycles, however, the terms detritivore and decomposer are often used interchangeably. Detritivores are an important aspect of many ecosystems and they can live on any soil with an organic component, including marine ecosystems, where they are termed interchangeably with bottom feeders. The eating of wood, whether alive or dead, is known as xylophagy, Τhe activity of animals feeding only on dead wood is called sapro-xylophagy and those animals, sapro-xylophagous. In food webs, detritivores generally play the roles of decomposers, detritivores are often eaten by consumers and therefore commonly play important roles as recyclers in ecosystem energy flow and biogeochemical cycles. Many detritivores live in woodland, though the term can be applied to certain bottom-feeders in wet environments. These organisms play a role in benthic ecosystems, forming essential food chains. Fungi, acting as decomposers, are important in todays terrestrial environment, by feeding on sediments directly to extract the organic component, some detritivores accidentally concentrate toxic pollutants. Decomposer Saprotrophic nutrition Nepenthes ampullaria Consumer-resource systems

Detritivore
–
Earthworms are a good example of soil-dwelling detritivores.
Detritivore
–
Two Common Bluebutterflies lap at a small lump of feces lying on a rock.
Detritivore
–
Fungi are the primary decomposers in most environments, illustrated here Mycena interrupta. Only fungi produce the enzymes necessary to decompose lignin, a chemically complex substance found in wood.
Detritivore
–
A decaying tree trunk in Canada's boreal forest. Decaying wood fills an important ecological niche, providing habitat and shelter, and returning important nutrients to the soil after undergoing decomposition.

70.
Saaremaa
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Saaremaa is the largest island in Estonia, measuring 2,673 km2. The main island of Saare County, it is located in the Baltic Sea, south of Hiiumaa island, the capital of the island is Kuressaare, which has about 15,000 inhabitants, the whole island has over 30,966 inhabitants. The island is called Saaremaa in Estonian, and in Finnish Saarenmaa — literally isle land or island land. In old Scandinavian sagas, Saaremaa is called Eysysla and in the Icelandic Sagas Eysýsla, which exactly the same as the name of the island in Estonian. This is the origin of the name in Danish Øsel, German and Swedish, Ösel, Gutnish Oysl. The name Eysysla appears sometimes together with Adalsysla, the big land, perhaps Suuremaa or Suur Maa in Estonian, in Latvian, the island is called Sāmsala, which means the island of Saami. According to archaeological finds, the territory of Saaremaa has been inhabited from at least 5,000 years BCE, pre-Viking age Salme ships burial have been found in Sõrve Peninsula. Sagas talk about numerous skirmishes between islanders and Vikings, Saaremaa was the wealthiest county of ancient Estonia and the home of notorious Estonian pirates, sometimes called the Eastern Vikings. The Chronicle of Henry of Livonia describes a fleet of sixteen ships, in 1206, King Valdemar II of Denmark built a fortress on the island but found no volunteers to man it. The Danes burned it themselves and left, probably around 1000, Gunnar Hámundarson from Iceland took part in a Viking raid at Eysýsla. There he obtained his famous atgeir, by taking it from a man named Hallgrímur, njáls saga tells the following, Thence they held on south to Denmark and thence east to Smálönd and had victory wherever they went. They did not come back in autumn, the next summer they held on to Rafala and fell in there with sea-rovers, and fought at once, and won the fight. After that they steered east to Eysýsla and lay there somewhile under a ness, there they saw a man coming down from the ness above them, Gunnar went on shore to meet the man, and they had a talk. Gunnar asked him his name, and he said it was Tófi, Gunnar asked again what he wanted. Thee I want to see, says the man, two warships lie on the other side under the ness, and I will tell thee who command them, two brothers are the captains — ones name is Hallgrímur, and the others Kolskeggur. I know them to be mighty men of war, and I know too that they have good weapons that the like are not to be had. Hallgrímur has an atgeir which he had made by seething-spells, and this is what the spells say, in 1227, Saaremaa was conquered by the Livonian Brothers of the Sword during the Livonian Crusade but remained a hotbed of Estonian resistance. The crusaders founded the Bishopric of Ösel-Wiek there, when the Order was defeated by the Lithuanian army in the Battle of Saule in 1236, the Saaremaa islanders rebelled

71.
PubMed Identifier
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PubMed is a free search engine accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. The United States National Library of Medicine at the National Institutes of Health maintains the database as part of the Entrez system of information retrieval, from 1971 to 1997, MEDLINE online access to the MEDLARS Online computerized database primarily had been through institutional facilities, such as university libraries. PubMed, first released in January 1996, ushered in the era of private, free, home-, the PubMed system was offered free to the public in June 1997, when MEDLINE searches via the Web were demonstrated, in a ceremony, by Vice President Al Gore. Information about the journals indexed in MEDLINE, and available through PubMed, is found in the NLM Catalog. As of 5 January 2017, PubMed has more than 26.8 million records going back to 1966, selectively to the year 1865, and very selectively to 1809, about 500,000 new records are added each year. As of the date,13.1 million of PubMeds records are listed with their abstracts. In 2016, NLM changed the system so that publishers will be able to directly correct typos. Simple searches on PubMed can be carried out by entering key aspects of a subject into PubMeds search window, when a journal article is indexed, numerous article parameters are extracted and stored as structured information. Such parameters are, Article Type, Secondary identifiers, Language, publication type parameter enables many special features. As these clinical girish can generate small sets of robust studies with considerable precision, since July 2005, the MEDLINE article indexing process extracts important identifiers from the article abstract and puts those in a field called Secondary Identifier. The secondary identifier field is to store numbers to various databases of molecular sequence data, gene expression or chemical compounds. For clinical trials, PubMed extracts trial IDs for the two largest trial registries, ClinicalTrials. gov and the International Standard Randomized Controlled Trial Number Register, a reference which is judged particularly relevant can be marked and related articles can be identified. If relevant, several studies can be selected and related articles to all of them can be generated using the Find related data option, the related articles are then listed in order of relatedness. To create these lists of related articles, PubMed compares words from the title and abstract of each citation, as well as the MeSH headings assigned, using a powerful word-weighted algorithm. The related articles function has been judged to be so precise that some researchers suggest it can be used instead of a full search, a strong feature of PubMed is its ability to automatically link to MeSH terms and subheadings. Examples would be, bad breath links to halitosis, heart attack to myocardial infarction, where appropriate, these MeSH terms are automatically expanded, that is, include more specific terms. Terms like nursing are automatically linked to Nursing or Nursing and this important feature makes PubMed searches automatically more sensitive and avoids false-negative hits by compensating for the diversity of medical terminology. The My NCBI area can be accessed from any computer with web-access, an earlier version of My NCBI was called PubMed Cubby

PubMed Identifier
–
PubMed

72.
Brittonia
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The New York Botanical Garden is a botanical garden and National Historic Landmark located in the Bronx, New York City. The 250-acre sites verdant landscape supports over one million living plants in extensive collections, the Garden is also a major educational institution. NYBG operates one of the worlds largest plant research and conservation programs, the Lorillard family owned most of the land that later became the New York Botanical Garden. That land and adjacent acreage was acquired by the City of New York and set aside for the creation of a zoo and botanical garden. The Garden was established on 28 April 1891 on part of the grounds of the Lorillard Estate and it was declared a National Historic Landmark in 1967. The Garden contains 50 different gardens and plant collections, there is a serene cascade waterfall, as well as wetlands and a 50-acre tract of original, never-logged, old-growth New York forest. The forest, which was never logged, contains oaks, American beeches, cherry, birch, tulip and white ash trees, some more than two centuries old. The forest itself is split by the Bronx River, the fresh water river in New York City. Along the shores sits the landmark Stone Mill, previously known as the Lorillard Snuff Mill built in 1840, sculptor Charles Tefft created the Fountain of Life on the grounds in 1905. It was conceived in the spirit of Italian baroque fountains, with the movement of galloping horses. The laboratory is a research institution, with projects more diverse than research in universities. The laboratorys research emphasis is on plant genomics, the study of how genes function in plant development, one question scientists hope to answer is Darwins abominable mystery, when, where, and why flowering plants emerged. The laboratorys research also furthers the discipline of molecular systematics, the study of DNA as evidence that can reveal the evolutionary history, a staff of 200 trains 42 doctoral students at a time, from all over the world. Since the 1890s, scientists from The New York Botanical Garden have mounted about 2,000 exploratory missions worldwide to collect plants in the wild. At the Pfizer Plant Research Laboratory, genomic DNA from many different species of plants is extracted to create a library of the DNA of the worlds plants. This collection is stored in a 768-square-foot DNA storage room with 20 freezers housing millions of specimens, including rare, to protect the collection during winter power outages, there is a backup 300-kilowatt electric generator. The Alfred P. Sloan Foundation has granted the NYBG $572,000 to begin a project called TreeBOL, the Tree Barcode of Life. Prominent civic leaders and financiers, including Andrew Carnegie, Cornelius Vanderbilt, founded in 1899, the LuEsther T. Mertz Library is the largest, most comprehensive botanical library in the Americas

73.
JSTOR
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JSTOR is a digital library founded in 1995. Originally containing digitized back issues of journals, it now also includes books and primary sources. It provides full-text searches of almost 2,000 journals, more than 8,000 institutions in more than 160 countries have access to JSTOR, most access is by subscription, but some older public domain content is freely available to anyone. William G. Bowen, president of Princeton University from 1972 to 1988, JSTOR originally was conceived as a solution to one of the problems faced by libraries, especially research and university libraries, due to the increasing number of academic journals in existence. Most libraries found it prohibitively expensive in terms of cost and space to maintain a collection of journals. By digitizing many journal titles, JSTOR allowed libraries to outsource the storage of journals with the confidence that they would remain available long-term, online access and full-text search ability improved access dramatically. Bowen initially considered using CD-ROMs for distribution, JSTOR was initiated in 1995 at seven different library sites, and originally encompassed ten economics and history journals. JSTOR access improved based on feedback from its sites. Special software was put in place to make pictures and graphs clear, with the success of this limited project, Bowen and Kevin Guthrie, then-president of JSTOR, wanted to expand the number of participating journals. They met with representatives of the Royal Society of London and an agreement was made to digitize the Philosophical Transactions of the Royal Society dating from its beginning in 1665, the work of adding these volumes to JSTOR was completed by December 2000. The Andrew W. Mellon Foundation funded JSTOR initially, until January 2009 JSTOR operated as an independent, self-sustaining nonprofit organization with offices in New York City and in Ann Arbor, Michigan. JSTOR content is provided by more than 900 publishers, the database contains more than 1,900 journal titles, in more than 50 disciplines. Each object is identified by an integer value, starting at 1. In addition to the site, the JSTOR labs group operates an open service that allows access to the contents of the archives for the purposes of corpus analysis at its Data for Research service. This site offers a facility with graphical indication of the article coverage. Users may create focused sets of articles and then request a dataset containing word and n-gram frequencies and they are notified when the dataset is ready and may download it in either XML or CSV formats. The service does not offer full-text, although academics may request that from JSTOR, JSTOR Plant Science is available in addition to the main site. The materials on JSTOR Plant Science are contributed through the Global Plants Initiative and are only to JSTOR

JSTOR
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The JSTOR front page

74.
International Standard Serial Number
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An International Standard Serial Number is an eight-digit serial number used to uniquely identify a serial publication. The ISSN is especially helpful in distinguishing between serials with the same title, ISSN are used in ordering, cataloging, interlibrary loans, and other practices in connection with serial literature. The ISSN system was first drafted as an International Organization for Standardization international standard in 1971, ISO subcommittee TC 46/SC9 is responsible for maintaining the standard. When a serial with the content is published in more than one media type. For example, many serials are published both in print and electronic media, the ISSN system refers to these types as print ISSN and electronic ISSN, respectively. The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers, as an integer number, it can be represented by the first seven digits. The last code digit, which may be 0-9 or an X, is a check digit. Formally, the form of the ISSN code can be expressed as follows, NNNN-NNNC where N is in the set, a digit character. The ISSN of the journal Hearing Research, for example, is 0378-5955, where the final 5 is the check digit, for calculations, an upper case X in the check digit position indicates a check digit of 10. To confirm the check digit, calculate the sum of all eight digits of the ISSN multiplied by its position in the number, the modulus 11 of the sum must be 0. There is an online ISSN checker that can validate an ISSN, ISSN codes are assigned by a network of ISSN National Centres, usually located at national libraries and coordinated by the ISSN International Centre based in Paris. The International Centre is an organization created in 1974 through an agreement between UNESCO and the French government. The International Centre maintains a database of all ISSNs assigned worldwide, at the end of 2016, the ISSN Register contained records for 1,943,572 items. ISSN and ISBN codes are similar in concept, where ISBNs are assigned to individual books, an ISBN might be assigned for particular issues of a serial, in addition to the ISSN code for the serial as a whole. An ISSN, unlike the ISBN code, is an identifier associated with a serial title. For this reason a new ISSN is assigned to a serial each time it undergoes a major title change, separate ISSNs are needed for serials in different media. Thus, the print and electronic versions of a serial need separate ISSNs. Also, a CD-ROM version and a web version of a serial require different ISSNs since two different media are involved, however, the same ISSN can be used for different file formats of the same online serial

International Standard Serial Number
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ISSN encoded in an EAN-13 barcode with sequence variant 0 and issue number 5

75.
Quaternary
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Quaternary is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy. It follows the Neogene Period and spans from 2.588 ±0.005 million years ago to the present, the Quaternary Period is divided into two epochs, the Pleistocene and the Holocene. The informal term Late Quaternary refers to the past 0. 5–1.0 million years, the Quaternary Period is typically defined by the cyclic growth and decay of continental ice sheets driven by Milankovitch cycles and the associated climate and environmental changes that occurred. The term Quaternary was proposed by Giovanni Arduino in 1759 for alluvial deposits in the Po River valley in northern Italy and it was introduced by Jules Desnoyers in 1829 for sediments of Frances Seine Basin that seemed clearly to be younger than Tertiary Period rocks. The Quaternary Period follows the Neogene Period and extends to the present, the Quaternary covers the time span of glaciations classified as the Pleistocene, and includes the present interglacial time-period, the Holocene. This places the start of the Quaternary at the onset of Northern Hemisphere glaciation approximately 2.6 million years ago, Quaternary stratigraphers usually worked with regional subdivisions. From the 1970s, the International Commission on Stratigraphy tried to make a single geologic time scale based on GSSPs, the Quaternary subdivisions were defined based on biostratigraphy instead of paleoclimate. This led to the problem that the base of the Pleistocene was at 1.805 Mya. The ICS then proposed to use of the name Quaternary altogether. The Anthropocene has been proposed as an epoch as a mark of the anthropogenic impact on the global environment starting with the Industrial Revolution. The Anthropocene is not officially designated by the ICS, however, the 2.6 million years of the Quaternary represents the time during which recognizable humans existed. Over this short period, there has been relatively little change in the distribution of the continents due to plate tectonics. The Quaternary geological record is preserved in detail than that for earlier periods. The climate was one of periodic glaciations with continental glaciers moving as far from the poles as 40 degrees latitude, there was a major extinction of large mammals in Northern areas at the end of the Pleistocene Epoch. Many forms such as saber-toothed cats, mammoths, mastodons, glyptodonts, others, including horses, camels and American cheetahs became extinct in North America. Glaciation took place repeatedly during the Quaternary Ice Age – a term coined by Schimper in 1839 that began with the start of the Quaternary about 2.58 Mya and continues to the present-day. In 1821, a Swiss engineer, Ignaz Venetz, presented an article in which he suggested the presence of traces of the passage of a glacier at a distance from the Alps. This idea was initially disputed by another Swiss scientist, Louis Agassiz, a year later, Agassiz raised the hypothesis of a great glacial period that would have had long-reaching general effects

76.
Holocene
–
The Holocene is the geological epoch that began after the Pleistocene at approximately 11,700 years before present. The term Recent has often used as an exact synonym of Holocene. The Holocene is part of the Quaternary period and its name comes from the Ancient Greek words ὅλος and καινός, meaning entirely recent. It has been identified with the current warm period, known as MIS1, given these, a new term, Anthropocene, is specifically proposed and used informally only for the very latest part of modern history involving significant human impact. It is accepted by the International Commission on Stratigraphy that the Holocene started approximately 11,700 years ago, the epoch follows the Pleistocene and the last glacial period. The Holocene can be subdivided into five time intervals, or chronozones, based on climatic fluctuations, Preboreal, Boreal, Atlantic, Subboreal and they find a general correspondence across Eurasia and North America, though the method was once thought to be of no interest. The scheme was defined for Northern Europe, but the changes were claimed to occur more widely. The periods of the include a few of the final pre-Holocene oscillations of the last glacial period. Paleontologists have not defined any faunal stages for the Holocene, if subdivision is necessary, periods of human technological development, such as the Mesolithic, Neolithic, and Bronze Age, are usually used. However, the time periods referenced by these terms vary with the emergence of those technologies in different parts of the world, climatically, the Holocene may be divided evenly into the Hypsithermal and Neoglacial periods, the boundary coincides with the start of the Bronze Age in Europe. According to some scholars, a division, the Anthropocene, has now begun. Continental motions due to plate tectonics are less than a kilometre over a span of only 10,000 years, however, ice melt caused world sea levels to rise about 35 m in the early part of the Holocene. The sea level rise and temporary land depression allowed temporary marine incursions into areas that are now far from the sea, Holocene marine fossils are known, for example, from Vermont and Michigan. Other than higher-latitude temporary marine incursions associated with depression, Holocene fossils are found primarily in lakebed, floodplain. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during the period exceeds any likely tectonic uplift of non-glacial origin, post-glacial rebound in the Scandinavia region resulted in the formation of the Baltic Sea. The region continues to rise, still causing weak earthquakes across Northern Europe, the equivalent event in North America was the rebound of Hudson Bay, as it shrank from its larger, immediate post-glacial Tyrrell Sea phase, to near its present boundaries. Climate has been stable over the Holocene. It appears that this was influenced by the glacial ice remaining in the Northern Hemisphere until the later date

77.
Pleistocene
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The Pleistocene is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the worlds most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period, the Pleistocene is the first epoch of the Quaternary Period or sixth epoch of the Cenozoic Era. In the ICS timescale, the Pleistocene is divided into four stages or ages, all of these stages were defined in southern Europe. In addition to this subdivision, various regional subdivisions are often used. Charles Lyell introduced the term pleistocene in 1839 to describe strata in Sicily that had at least 70% of their molluscan fauna still living today and this distinguished it from the older Pliocene Epoch, which Lyell had originally thought to be the youngest fossil rock layer. The Pleistocene has been dated from 2.588 million to 11,700 years before present and it covers most of the latest period of repeated glaciation, up to and including the Younger Dryas cold spell. The end of the Younger Dryas has been dated to about 9640 BC, the IUGS has yet to approve a type section, Global Boundary Stratotype Section and Point, for the upper Pleistocene/Holocene boundary. The proposed section is the North Greenland Ice Core Project ice core 75°06 N 42°18 W, the lower boundary of the Pleistocene Series is formally defined magnetostratigraphically as the base of the Matuyama chronozone, isotopic stage 103. Above this point there are notable extinctions of the calcareous nanofossils, Discoaster pentaradiatus, the Pleistocene covers the recent period of repeated glaciations. The name Plio-Pleistocene has, in the past, been used to mean the last ice age. The revised definition of the Quaternary, by pushing back the date of the Pleistocene to 2.58 Ma. Pleistocene climate was marked by repeated glacial cycles in which continental glaciers pushed to the 40th parallel in some places and it is estimated that, at maximum glacial extent, 30% of the Earths surface was covered by ice. In addition, a zone of permafrost stretched southward from the edge of the sheet, a few hundred kilometres in North America. The mean annual temperature at the edge of the ice was −6 °C, during interglacial times, such as at present, drowned coastlines were common, mitigated by isostatic or other emergent motion of some regions. The effects of glaciation were global, antarctica was ice-bound throughout the Pleistocene as well as the preceding Pliocene. The Andes were covered in the south by the Patagonian ice cap, there were glaciers in New Zealand and Tasmania. The current decaying glaciers of Mount Kenya, Mount Kilimanjaro, glaciers existed in the mountains of Ethiopia and to the west in the Atlas mountains. In the northern hemisphere, many glaciers fused into one, the Cordilleran ice sheet covered the North American northwest, the east was covered by the Laurentide

78.
Pliocene
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The Pliocene Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58 million years BP. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era, the Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch.588 to 1.806 million years ago, and is now included in the Pleistocene. As with other geologic periods, the geological strata that define the start and end are well identified but the exact dates of the start. The boundaries defining the Pliocene are not set at an easily identified worldwide event, the upper boundary was set at the start of the Pleistocene glaciations. The Pliocene was named by Sir Charles Lyell, the name comes from the Greek words πλεῖον and καινός and means roughly continuation of the recent, referring to the essentially modern marine mollusc faunas. H. W. Fowler called the term a regrettable barbarism, in the official timescale of the ICS, the Pliocene is subdivided into two stages. From youngest to oldest they are, Piacenzian Zanclean The Piacenzian is sometimes referred to as the Late Pliocene, in the system of North American Land Mammal Ages include Hemphillian, and Blancan. The Blancan extends forward into the Pleistocene, South American Land Mammal Ages include Montehermosan, Chapadmalalan and Uquian. In the Paratethys area the Pliocene contains the Dacian and Romanian stages, as usual in stratigraphy, there are many other regional and local subdivisions in use. In Britain the Pliocene is divided into the stages, Gedgravian, Waltonian, Pre-Ludhamian, Ludhamian, Thurnian, Bramertonian or Antian, Pre-Pastonian or Baventian, Pastonian and Beestonian. The exact correlations between these stages and the ICS stages is still a matter of detail. The formation of an Arctic ice cap is signaled by a shift in oxygen isotope ratios and ice-rafted cobbles in the North Atlantic. Mid-latitude glaciation was probably underway before the end of the epoch, the global cooling that occurred during the Pliocene may have spurred on the disappearance of forests and the spread of grasslands and savannas. Continents continued to drift, moving from positions possibly as far as 250 km from their present locations to positions only 70 km from their current locations, africas collision with Europe formed the Mediterranean Sea, cutting off the remnants of the Tethys Ocean. The border between the Miocene and the Pliocene is also the time of the Messinian salinity crisis, Sea level changes exposed the land-bridge between Alaska and Asia. Pliocene marine rocks are exposed in the Mediterranean, India. Elsewhere, they are exposed largely near shores, the change to a cooler, dry, seasonal climate had considerable impacts on Pliocene vegetation, reducing tropical species worldwide. Deciduous forests proliferated, coniferous forests and tundra covered much of the north, tropical forests were limited to a tight band around the equator, and in addition to dry savannahs, deserts appeared in Asia and Africa

Pliocene
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The gastropodOliva sayana, from the Pliocene of Florida.
Pliocene
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Mid-Pliocene reconstructed annual sea surface temperature anomaly
Pliocene
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The coralCladocora from the Pliocene of Cyprus.
Pliocene
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A gastropod and attached serpulid wormtube from the Pliocene of Cyprus.

79.
Early Jurassic
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The Early Jurassic epoch is the earliest of three epochs of the Jurassic period. The Early Jurassic starts immediately after the Triassic-Jurassic extinction event,201.3 Ma, certain rocks of marine origin of this age in Europe are called Lias and that name was used for the period, as well, in 19th century geology. In southern Germany rocks of this age are called Black Jurassic, there are extensive Liassic outcrops around the coast of the United Kingdom, in particular in Glamorgan, North Yorkshire and Dorset. The Jurassic Coast of Dorset is often associated with the work of Mary Anning of Lyme Regis. The facies of the Lower Jurassic in this area are predominantly of clays, thin limestones and siltstones, Lias Group strata form imposing cliffs on the Vale of Glamorgan coast, in southern Wales. There has been debate over the actual base of the Hettangian stage. If this biostratigraphical indicator is used, then technically the Lias Group—a lithostratigraphical division—spans the Jurassic / Triassic boundary, during this period, ammonoids, which had almost died out at the end-of-Triassic extinction, radiated out into a huge diversity of new forms with complex suture patterns. Ammonites evolved so rapidly, and their shells are so often preserved, there were several distinct waves of ammonite evolution in Europe alone. The Early Jurassic was an important time in the evolution of the marine reptiles, all these plesiosaurs had medium-sized necks and large heads. In the Toarcian, at the end of the Early Jurassic, accompanying them as small carnivores were the sphenosuchian and protosuchid crocodilians. In the air, new types of pterosaurs replaced those that had died out at the end of the Triassic, but in the undergrowth were various types of early mammals, as well as tritylodont mammal-like reptiles, lizard-like sphenodonts, and early Lissamphibians. Late Triassic Toarcian turnover Davies, A. M, an Introduction to Palaeontology, Thomas Murby & Co. Geology of The Dorset Coast, The Geologists Association, simms, M. J. Chidlaw, N. Morton, N. and Page, K. N. British Lower Jurassic Stratigraphy, Geological Conservation Review Series, No,30, Joint Nature Conservation Committee, Peterborough. Early Jurassic Period – The Lias epoch, informative lecture notes by Dr. Paul Olsen

80.
Guadalupian
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The Permian is a geologic period and system which spans 46.7 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic Period 252.2 Mya. It is the last period of the Paleozoic Era, the following Triassic Period belongs to the Mesozoic Era, the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the groups of the mammals, turtles, lepidosaurs. The world at the time was dominated by two known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior, amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors. The Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earths history, in which nearly 90% of marine species and it would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian-Triassic extinction event was protracted, on land, the term Permian was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil, the region now lies in the Perm Krai of Russia. This could have in part caused the extinctions of marine species at the end of the period by severely reducing shallow coastal areas preferred by many marine organisms. During the Permian, all the Earths major landmasses were collected into a supercontinent known as Pangaea. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, a new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmass interiors experience climates with extreme variations of heat and cold, deserts seem to have been widespread on Pangaea. Such dry conditions favored gymnosperms, plants with seeds enclosed in a cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian, the climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an Ice Age, glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continents interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles, Permian marine deposits are rich in fossil mollusks, echinoderms, and brachiopods. By the close of the Permian, trilobites and a host of other groups became extinct. Terrestrial life in the Permian included diverse plants, fungi, arthropods, the period saw a massive desert covering the interior of Pangaea

81.
Terreneuvian
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The Terreneuvian is the lowermost and oldest series of the Cambrian geological system. Its base is defined by the first appearance datum of the trace fossil Treptichnus pedum around 541 million years ago and its top is defined as the first appearance of trilobites in the stratigraphic record around 521 million years ago. This series was ratified by the International Commission on Stratigraphy in 2012. The Fortunian stage and presently unnamed Cambrian Stage 2 are the stages within this series, the Terreneuvian corresponds to the pre-trilobitic Cambrian. The name Terreneuvian is derived from Terre Neuve, a French name for the island of Newfoundland, Canada, the type locality of the Terreneuvian is in Fortune Head, at the northern edge of the Burin Peninsula, Newfoundland, Canada. The outcrops show a carbonate-siliciclastic succession which is mapped as the Chapel Island Formation, the Precambrian-Cambrian boundary lies 2.4 m above the base of the second member, which is the lowest occurrence of Treptichnus pedum. The traces can be seen on the surface of the sandstone layers. The first calcareous shelled skeletal fossils are 400 m above the boundary, the first trilobites appear 1400 m above the boundary, which corresponds to the beginning of the Branchian Series

Terreneuvian
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Delegates from the Ichnia 2012 conference inspect the Global Boundary Stratotype Section and Point (GSSP) for the Ediacaran-Cambrian boundary at Fortune Head Ecological Reserve, Newfoundland, Canada. The boundary is defined on the appearance of the complex, vertical trace fossil Treptichnus (formerly Phycodes) pedum.

82.
Tonian
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The Tonian is the first geologic period in the Neoproterozoic Era and lasted from 1000 Mya to 720 Mya. Instead of being based on stratigraphy, these dates are defined by the ICS based on radiometric chronometry, rifting leading to the breakup of supercontinent Rodinia, which had formed in the mid-Stenian, occurred during this period, starting from 900 to 850 Mya. The first large radiation of acritarchs occurred during the Tonian, the first Metazoans are found in the late Tonian some 800 MYA. A notable example of this is the poriferan-like species Otavia antiqua, archived from the original on May 12,2006. Status on Divisions of the International Geologic Time Scale

Tonian

83.
Siderian
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The Siderian Period is the first geologic period in the Paleoproterozoic Era and lasted from 2500 Ma to 2300 Ma. Instead of being based on stratigraphy, these dates are defined chronometrically, the laying down of the banded iron formations peaked early this period. BIFs were formed as anaerobic algae produced waste oxygen that combined with iron and this process cleared iron from the oceans, presumably turning greenish seas clear. Eventually, without an oxygen sink in the oceans, the process allowed the build up of an oxygen-rich atmosphere and this event is known as the oxygen catastrophe, which according to some geologists triggered the Huronian glaciation. But as of February 2017, this has not yet officially adopted by the IUGS

Siderian
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Banded iron formations were very common in this period.

84.
Eoarchean
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The Eoarchean is the first era of the Archean Eon of the geologic record for which the Earth has a solid crust. It spans 400 million years from the end of the Hadean Eon 4000 million years ago to the start of the Paleoarchean Era 3600 Mya, the abiotic origins of life have been dated to this era and evidence of cyanobacteria date to 3500 Mya, just outside of this era. At that time atmosphere was without oxygen and the pressure values ranged from 10 to 100 bar, the Eoarchean was formerly officially unnamed and informally referred to as the first part of the Early Archean or Paleoarchean Era, both now obsolete names. The Eoarchaeans lower boundary or starting point of 4 Gya is officially recognized by the International Commission on Stratigraphy, the name comes from two Greek words, eos and archaios. The first supercontinent Vaalbara appeared around the end of this period at about 3,600 million years ago, a characteristic of the Eoarchean is that Earth possessed a firm crust for the first time. However, this crust may have been incomplete at many sites, the beginning of the Eoarchean is characterized by heavy asteroid bombardment within the inner solar system, the Late Heavy Bombardment. The Eoarchean is the first time from which solid rock formations on Earth have survived, the largest is the Isua Greenstone Belt on the south-west coast of Greenland and dates from 3.8 billion years. The Acasta Gneiss within the Canadian Shield have been dated to be 4,030 Ma and are therefore the oldest preserved rock formations. In 2008, another rock formation was discovered in the Nuvvuagittuq greenstone belt in northern Québec Canada which has dated to be 4,280 million years ago. These formations are presently under intense investigation,3,850 million years old Greenland apatite shows evidence of 12C enrichment. This has sparked a debate whether there might have been photosynthetic life before 3.8 billion years, origins of Life, The Primal Self-Organization. Media related to Eoarchean at Wikimedia Commons Taxonconcept. stratigraphy. ne, A short fact sheet on the Eoarchean

85.
Mya (unit)
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A year is the orbital period of the Earth moving in its orbit around the Sun. Due to the Earths axial tilt, the course of a year sees the passing of the seasons, marked by changes in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the globe, four seasons are recognized, spring, summer, autumn. In tropical and subtropical regions several geographical sectors do not present defined seasons, but in the seasonal tropics, a calendar year is an approximation of the number of days of the Earths orbital period as counted in a given calendar. The Gregorian, or modern, calendar, presents its calendar year to be either a common year of 365 days or a year of 366 days, as do the Julian calendars. For the Gregorian calendar the average length of the year across the complete leap cycle of 400 years is 365.2425 days. The ISO standard ISO 80000-3, Annex C, supports the symbol a to represent a year of either 365 or 366 days, in English, the abbreviations y and yr are commonly used. In astronomy, the Julian year is a unit of time, it is defined as 365.25 days of exactly 86400 seconds, totalling exactly 31557600 seconds in the Julian astronomical year. The word year is used for periods loosely associated with, but not identical to, the calendar or astronomical year, such as the seasonal year, the fiscal year. Similarly, year can mean the period of any planet, for example. The term can also be used in reference to any long period or cycle, west Saxon ġēar, Anglian ġēr continues Proto-Germanic *jǣran. Cognates are German Jahr, Old High German jār, Old Norse ár and Gothic jer, all the descendants of the Proto-Indo-European noun *yeh₁rom year, season. Cognates also descended from the same Proto-Indo-European noun are Avestan yārǝ year, Greek ὥρα year, season, period of time, Old Church Slavonic jarŭ, Latin annus is from a PIE noun *h₂et-no-, which also yielded Gothic aþn year. Both *yeh₁-ro- and *h₂et-no- are based on verbal roots expressing movement, *h₁ey- and *h₂et- respectively, the Greek word for year, ἔτος, is cognate with Latin vetus old, from the PIE word *wetos- year, also preserved in this meaning in Sanskrit vat-sa- yearling and vat-sa-ras year. Derived from Latin annus are a number of English words, such as annual, annuity, anniversary, etc. per annum means each year, anno Domini means in the year of the Lord. No astronomical year has an number of days or lunar months. Financial and scientific calculations often use a 365-day calendar to simplify daily rates, in the Julian calendar, the average length of a year is 365.25 days. In a non-leap year, there are 365 days, in a year there are 366 days

Mya (unit)
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Key concepts

86.
Integrated Authority File
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The Integrated Authority File or GND is an international authority file for the organisation of personal names, subject headings and corporate bodies from catalogues. It is used mainly for documentation in libraries and increasingly also by archives, the GND is managed by the German National Library in cooperation with various regional library networks in German-speaking Europe and other partners. The GND falls under the Creative Commons Zero license, the GND specification provides a hierarchy of high-level entities and sub-classes, useful in library classification, and an approach to unambiguous identification of single elements. It also comprises an ontology intended for knowledge representation in the semantic web, available in the RDF format